Chocolate Cake Traybake!

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Thick Chocolate Cake Traybake, with Thick Chocolate Frosting! Perfect for Parties, or Occasions, or anything!

I haven’t done too many traybake recipes in my time, if you talk about cake style traybakes. The other side, the Brownies, Blondies, Rocky Roads etc I have done almost too many to count (whether the recipes made it to the blog or not), but cake wise? Only a few. This is for any particular reason to be honest, just because I never thought they were very ‘wow’.

To be fair, I am completely wrong. I often get requests for a cake like this, and I just haven’t really got round to it till now! When I posted my Carrot Cake Traybake in March, it was SUCH a big hit! I honestly didn’t expect it, and it was a bit of a random one to plug some days up in the run up to Easter, but I regret not posting it sooner!

I thought originally “oh its just a cake that you give out at a party, if you don’t want the centrepiece cake too big”, which is actually often a thing. People create a ‘cutting cake’ if they don’t want, or can’t have the actual wedding cake for example that massive. I just didn’t realise that people like making them at home so much!

When I have asked in the past for requests of recipes, I usually get really out there ones that are almost a bit too specific for my blog, or ones that I have done, or ones that I would happily do. But quite often or not, there are ones that are just basic bakes that I have managed to have not done already, or ones that completely passed my mind like this one!

When starting this recipe I wanted to make sure that it was going to be delicious. When you have a traybake cake, there is NO WHERE to hide. You can’t layer it up and make it look that pretty, and its so big that its awkward to try and cover up in some way. I wanted to make sure that the cake was suitably fudgey, and delicious, like the ‘traybake cakes’ that you can buy for parties in the supermarket.

You can easily do it with a straight forward Victoria sponge style sponge but I just think if you really are only leaving it as is, with some frosting on top, then I wanted it a smidge denser to make it more delicious. I ended up basing it on my Chocolate Fudge Cake Recipe, but slightly altered to fit the tin better!

Because this sponge uses Coffee, and Buttermilk, it creates the most wonderful thick gooey sponge that everyone wants to devour. Trust me, YOU CAN’T TASTE THE COFFEE, and it just enhances the chocolate flavour so I would 100000% recommend sticking with it! Honestly, you’ll regret it if you don’t. You can use actual espresso, or instant coffee etc, but anything dissolved in 125ml of water will do.

The Frosting for the cake is also from my Chocolate Fudge Cake recipe, as its just personally the best chocolate frosting on the planet ever. This is optional, you could easily use just melted chocolate, or a ganache type frosting, but I really wanted a good solid frosting instead that is usually a crowd pleaser, and from the comments I have received in the past, this is the frosting to choose!

You can decorate it how you want, but I just went for some sprinkles and some small chocolate bits and it’s all done! Cut up into squares and enjoy! x

Chocolate Sheet Cake!

Thick Chocolate Sheet Cake Traybake, with Thick Chocolate Frosting! Perfect for Parties, or Occasions, or anything!
4.93 from 14 votes
Print Pin Rate
Category: Cake
Type: Traybakes
Keyword: Chocolate
Prep Time: 15 minutes
Cook Time: 55 minutes
Total Time: 50 minutes
Servings: 20 Servings
Author: Jane's Patisserie



  • 250 g Dark Chocolate
  • 250 g Unsalted Butter
  • 1 tbsp Instant Coffee
  • 125 ml Boiling Water
  • 200 g Plain Flour
  • 50 g Cocoa Powder
  • 1.5 tsp Baking Powder
  • 1/2 tsp Bicarbonate of Soda
  • 250 g Caster Sugar
  • 250 g Light Brown Sugar
  • 4 Large Eggs
  • 100 ml Buttermilk


  • 250 g Unsalted Butter (room temp)
  • 500 g Icing Sugar
  • 50 g Cocoa Powder
  • 100-125 ml Evaporated Milk
  • 1 tsp Vanilla Extract


  • Sprinkles
  • Chocolate Curls


For the Cake

  • Preheat your oven to 160/140C Fan, and line a 9x13" Tin with parchment paper. 
  • In a heatproof bowl, microwave the Dark Chocolate & Butter till melted – mine takes two minutes! 
  • Pour the Coffee Granules into 125ml Boiling Water and mix – add the coffee to the Chocolate/Butter mix and stir well till smooth!
  • In a separate large bowl add the Plain Flour, Cocoa Powder, Baking Powder, Bicarbonate of Soda, Golden Caster Sugar, and Light Brown Sugar and mix well so the ingredients are all mixed with each other well!
  • Mix the Eggs with the Buttermilk – Add the Chocolate Mix & the Egg Mix to the dry ingredients and stir together, try not to over mix it – you don't need to use an electric mixer, just use a bowl and a spatula. 
  • Pour the mixture into the tin and bake in the oven for 50-60 minutes (can take a little longer in some ovens) once baked leave to cool in the tin and remove afterwards, or leave for 10-15 minutes and cool on a wire rack for a softer cake.

For the Frosting

  • With an electric mixer with the paddle attachment, beat the butter until its very smooth and supple (couple of minutes)
  • Gradually add the Icing Sugar & Cocoa Powder alternatively with the Evaporated Milk until all is incorporated and add the vanilla essence – beat for a couple of minutes so its extra smooth & creamy.
  • The more evaporated milk you add the more runny it’ll be, and I have found about 100ml-125ml is perfect for me! Decorate your cake how you like and ENJOY!


  • This cake will last for 3 days at room temperature. 
  • This Is The Cake Tin I Used 
  • I 100% would stick with using the coffee in the cake, you can't taste it, but it helps the chocolate flavour so is important. 
  • The cake can take longer to bake if its over mixed - be as gentle as possible with it. 
  • If you can't access Buttermilk, you can make your own by using 100ml of FULL FAT Milk, mixed with 2tbsp of Lemon Juice! It will look curdled but this is fine. 
Nutrition Facts
Chocolate Sheet Cake!
Amount Per Serving
Calories 472 Calories from Fat 243
% Daily Value*
Fat 27g42%
Saturated Fat 16g100%
Cholesterol 93mg31%
Sodium 67mg3%
Potassium 281mg8%
Carbohydrates 67g22%
Fiber 3g13%
Sugar 52g58%
Protein 5g10%
Vitamin A 705IU14%
Vitamin C 0.1mg0%
Calcium 74mg7%
Iron 3mg17%
* These are only estimates and can vary dependant on brands of ingredients and serving sizes.


Find my other Recipes on my Recipes Page!

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About Author

Hiya! I'm Jane, and I adore baking, cooking and all things delicious. I'm also partial to homewares, lifestyle posts and more!


  • Kat
    September 6, 2020 at 5:35 pm

    5 stars
    Absolutely delicious! Thank you!

  • Carmen
    August 18, 2020 at 9:47 pm

    Are you able to pipe the frosting into flowers onto the cake or will it be too soft?

    • Jane's Patisserie
      August 19, 2020 at 12:01 pm

      I would say this frosting is too soft xx

  • Danielle
    August 15, 2020 at 5:49 pm

    Hi Jane I can only find a 9×12 traybake tin will this be ok to use with same measurements for ingredients? X

    • Jane's Patisserie
      August 15, 2020 at 8:08 pm

      Yes that should okay, may take a smidge longer to bake x

  • CC
    August 14, 2020 at 7:06 pm

    Hi Jane
    This looks delicious. Do you think it will work with fondant on top? I need to bake a Traybake with a theme for a party.

    • Jane's Patisserie
      August 14, 2020 at 8:49 pm

      The frosting is quite soft, but if you are just putting a layer on top it may be okay..!

  • Ruth
    August 8, 2020 at 9:10 pm

    Have been baking during lockdown for various charities and found you through one of the other bakers. Have made so many of your tray bakes for NHS and vulnerable people. They are all so good. Made this one yesterday. OMG so good. Want to make another one with the buttermilk and evaporated milk that I have left over. Does the cake freeze well? Obviously without the frosting..

    • Jane's Patisserie
      August 9, 2020 at 12:27 pm

      Hey! Yes it does freeze well!! And I’m so glad! xx

  • Claudia
    August 7, 2020 at 4:38 pm

    5 stars
    Hi Jane!

    Just 1 more question if that’s okay – Is there anything I can do or any changes you would reccomend i make to prevent the cake from coming out of the oven more like a moist brownie?? (Tastes AMAZING still – but wanted it fluffier like yours)

    Thank you so much x

    • Jane's Patisserie
      August 8, 2020 at 12:13 pm

      If a cake is dense it usually means it needed longer baking – although the texture of this sort of fudge cake is denser than a normal sponge! xx

  • Claudia
    August 6, 2020 at 5:33 pm

    Hi Jane!

    Would i be able to double the ingredients to make this 2 tier? Or would you advise against this?

    Thank you!

    • Jane's Patisserie
      August 6, 2020 at 6:20 pm

      You would need to bake the sponges separately, and it is quite deep so that would be a whole lotta cake!! x

  • Katrina Scammell
    August 3, 2020 at 7:24 am

    5 stars
    This is the 2nd cake I’ve made from this site. This one was just as good. It was lovely and I will make again. It didn’t last long and it was all adults no children. Next cake I’m trying is the biscoff cake for a birthday next week.

  • Amy N
    August 2, 2020 at 9:28 am

    Hi, I absolutely love your recipes so going to give this one a go today as I love your chocolate fudge cupcake recipe! I only have either a 9×9 or 8×10 tin.. would you adapt the recipe or the cooking time? X

    • Jane's Patisserie
      August 2, 2020 at 6:25 pm

      I would use maybe 2/3 of the recipe? I’m not sure on timings but it would definitely be less x

  • Emma
    July 30, 2020 at 4:03 pm

    Hi Jane,

    I am having trouble getting hold of light brown sugar at the moment – is there another sugar that I could use instead?

    • Jane's Patisserie
      July 30, 2020 at 7:53 pm

      Caster sugar, golden caster or dark brown sugar! x

  • Danielle
    July 13, 2020 at 8:14 pm

    Can I use stork instead of butter in the cake?

  • Terrie
    June 25, 2020 at 8:02 pm

    Hi, just wondered what you do with the rest of the evaporated milk? Thanks

    • Jane's Patisserie
      June 25, 2020 at 9:24 pm

      You can freeze it! I often buy the mini tubs so there’s less leftover!

    • Terrie
      June 27, 2020 at 8:29 am

      That’s great thank you. I could only get a big 400ml tin and didn’t want the rest to go to waste. Your recipes are amazing!

    • Jemma
      July 19, 2020 at 12:42 pm

      5 stars
      Could you please recommend a gluten free switch? 🙂

  • Lara
    June 2, 2020 at 2:33 pm

    5 stars
    I made this with 125g of brown sugar instead of full amount, as I always try to reduce sugar a bit as find it too sweet., it turned out perfect – soft delicate very chocolaty cake, still very sweet. I will try to reduce the caster sugar next time and post how it goes for those that may be interested 🙂 I didn’t ice it this time.

  • Jayne
    May 19, 2020 at 9:16 pm

    Hi Jane, can I used this recipe in cake tins instead of a traybake? Thank you I love all your recipes! Xxx

    • Jane's Patisserie
      May 20, 2020 at 9:25 am

      Have a look at my chocolate fudge cake recipe as that is already a round cake version!

  • Kasia
    May 17, 2020 at 4:46 pm

    Hi Jane,
    I baked that cake for my son’s birthday as he is chocolate fun. My family loved it and my both kids couldn’t stop eating the cake. 🙂 Thanks for the recipe, definitely I’ll try some other cakes. xx

    • Jane's Patisserie
      May 18, 2020 at 11:22 am

      Ahh yay! Amazing! I love these sort of cakes for kids birthdays! x

  • Emma McCutcheon
    May 11, 2020 at 1:53 pm

    Hi Jane!

    Massive fan of your recipes!

    A very silly question, I believe there used to be calories on the recipes but I can’t seem to find it anymore.

    Have they been taken away?

    Thank you!

  • Amy
    May 10, 2020 at 11:00 am

    Love this recipe but can you freeze the cake?

  • Gaynor
    May 9, 2020 at 2:00 pm

    I made this gluten free by just substituting the flour for gf but it was a bit of a disaster. It was in the oven for 1hr 20mins but still didn’t really seem to cook, don’t know whether adding Xanthan Gum would have made a difference. It tasted nice though. Kids had it with custard as it was too uneven and soft to ice.

    • Jane's Patisserie
      May 9, 2020 at 2:35 pm

      Unfortunately, this cake is very delicate as it is and probably isn’t a simple switch no. I would have suggested adding xantham gum. If you ever want to know about switches I recommend asking first just in case!

  • Mary D
    May 4, 2020 at 10:31 pm

    Can I pipe with the frosting instead or is it too runny of a consistency to pipe with?

    • Jane's Patisserie
      May 5, 2020 at 9:02 am

      It can be piped as I use the same for my chocolate fudge cupcakes, but it’s definitely a softer consistency than normal. You MUST use real butter, and not any form of spread, otherwise it will be way way too soft!

  • Jane mcintosh
    October 19, 2019 at 8:13 pm

    Made this today mines took 55mins to cook. but sunk a little in middle, but when icing went on you wouldn’t notice well what can I say it was absolutely beautiful didn’t even taste the coffee (I detest coffee) will definitely be making again

  • Rowena Derbyshire
    October 6, 2019 at 9:13 am

    Hi, my husband is pre-diabetic so has to be careful not to have too much sugar. Do you think this would work if I used wholemesl self raiding & Coconut sugar or Total Sweet xylitol in the cake? I’d prob make a thinner icing. Or any other suggestions for a birthday cake?

    • Jane's Patisserie
      October 6, 2019 at 7:33 pm

      I would advise looking for a recipe specific to low sugar/no sugar as it’s quite key to this one!

  • Mikki
    September 25, 2019 at 5:41 pm

    5 stars
    oh my goodness 😍 what a great recipe for a chocolate cake!! I’ve been baking at home for years but never thought of adding evaporated milk to buttercream… YUM!! I found my cake took about 15 mins longer to bake than recommended at 140°. Will definately be baking this one again 😁

  • Nina
    September 3, 2019 at 7:13 am

    Hi, will this work with sour cream?

    • Jane's Patisserie
      September 3, 2019 at 7:34 am

      I would recommend buttermilk as the recipe says for the best bake.

  • Megan Kane
    July 8, 2019 at 3:51 pm

    5 stars
    Hey Jane,

    I attempted this last night and although the cake is moist and tastes amazing, it sunk in the middle and just falls to bit when you try and pick it up. What have I done wrong and how can I fix it for next time? Thank you! X

    • Jane's Patisserie
      July 8, 2019 at 4:16 pm

      If it sunk in the middle it probably wasn’t quite finished baking – the cake is very delicate as well but that’s part of its delicious charm! x

  • Jill
    June 3, 2019 at 4:05 pm

    These look amazing and I can’t wait to make. My mums coeliac so as usual for us they’ll be gf. Have you made this traybake gf before? Can’t decide between these and some of your other gf recipes! I know you’ve quite recently given up gluten so if need any hints or tips on the best products etc then let me know. Xxx

    • Jane's Patisserie
      June 3, 2019 at 7:39 pm

      Hiya – I haven’t recently given up gluten, I still eat it! You could definitely try it GF however, but I haven’t with this one in particular. You would need to add in xantham gum to stabilise the mixture before, but it will most likely be extremely soft without the gluten so beware!

  • Rhian
    February 8, 2019 at 5:04 pm

    Hi, can you tell me if i can use an alternative to the buttermilk? I cant have dairy ( i can adapt everything else) didn’t know if i can use almond milk instead? thanks.

    • Jane's Patisserie
      February 8, 2019 at 8:56 pm

      I’m afraid I am unsure of a dairy alternative to buttermilk – I would advise looking at a dairy free cake such as mine and covert that into a traybake!

    • Hani
      March 13, 2019 at 6:05 pm

      i think u can use any other dairy free milk and add vinegar to make a buttermilk substitute

  • Sophie
    December 17, 2018 at 6:34 pm

    5 stars

    Can you tell me how deep the cake tin needs to be? Thank you!

    • Jane's Patisserie
      December 17, 2018 at 6:44 pm

      Hiya! I think mine is 2-2.5″ deep! Most traybake size tins are similar! x

  • Penni
    December 10, 2018 at 9:55 pm

    4 stars
    Hi Jane, please could you tell me what the oven temperature is for this delicious cake? My cake seemed to come out a little raw 🙁 still lovely though!

    • Jane's Patisserie
      December 11, 2018 at 9:16 am

      Its 160C, or 140C for a fan oven – as mentioned, it can take longer for some ovens to bake the cake. If it’s raw, it wasn’t finished baking.

  • Jenny
    December 7, 2018 at 5:12 pm

    5 stars
    I often find that the supermarket traybakes are quite dry, so i’m definitely trying this! I just found your website and it has given me so many ideas x

  • Soph
    November 10, 2018 at 2:18 pm

    I’m not really a fan of dark chocolate (too strong)
    Can I use milk Chocolate instead?

    • Jane's Patisserie
      November 10, 2018 at 5:13 pm

      You can’t taste it once it’s baked into the cake, I would only use dark chocolate. It makes it delicious, and it’s not too dark after.

  • Danielle
    October 3, 2018 at 4:59 pm

    I tried this today and was very excited but something has gone wrong. I opened my oven after 40mins and my cake seems as though it has sunk but the middle section is crispy. Do you have an idea what I have done wrong 😞

    • Jane's Patisserie
      October 4, 2018 at 8:41 am

      I think you opened the oven too early, so it sunk and baked weirdly. The temperature can change up to 10 degrees for every second the oven is open, so if it was too early for the bake it would have affected it quite badly!

  • Elizabeth
    September 29, 2018 at 7:29 pm

    5 stars
    Hi Jane,
    This is the first recipe I’ve made from your blog and I think I will have to try lots more! It was absolutely beautiful and I got so many compliments on it. My frosting was a lot paler than yours, I wonder if I did anything wrong? But it tasted amazing anyway

    • Jane's Patisserie
      September 29, 2018 at 7:48 pm

      It was probably down to the cocoa powder – which one did you use? x

    • Elizabeth
      September 29, 2018 at 8:40 pm

      All I had was some from Lidl, that was probably it! Thanks x

    • Jane's Patisserie
      September 30, 2018 at 9:20 am

      Sometimes some just aren’t as dark or as chocolatey! I use Tescos own, and it looks so much darker than bournville for example! xx

  • Stephanie Bawden
    September 27, 2018 at 3:48 pm

    5 stars
    This was amazing thank you Jane! Made if for 2 work colleagues leaving today & added smarties & maltesers for decoration – just incase there wasn’t enough chocolate already lol! Loads of posititve comments from my work mates & not much left when I left mid afternoon!
    Any chance you could do a recipe for a similar traybake but with no chocolate (or white chocolate) as my husband gets migranes from milk & plain chocolate & missed out on the deliciousness! Thanks a million

    • Jane's Patisserie
      September 28, 2018 at 9:45 am

      Hiya! I have other recipes scheduled in, but I don’t like post similar recipes like this too close together so it is coming! But I’m glad this one was enjoyed!!

  • Kathleen
    September 16, 2018 at 9:36 pm

    5 stars
    Hi – loving your blog. Think you might want to check your U.S. conversions from Metric on this recipe as they seem all over the place e.g. sugar, coffee, and bicarb.

    • Jane's Patisserie
      September 17, 2018 at 12:11 pm

      It’s all done automatically, I don’t do the conversions myself.

    • Reeya
      June 1, 2019 at 12:43 pm

      Can I cut out one of the sugars as in just put 250g instead of 500?

    • Jane's Patisserie
      June 2, 2019 at 9:13 am

      I wouldn’t advise it – to get what’s in the pictures, you need to use the recipe.

  • doris stuart
    September 16, 2018 at 1:14 pm

    cake looks good but i t drink coffee so i wont go get coffee to make this cake. i can tell there something different when added coffee/ cuz friend made cupcakes using coffee and i could tell theres a different in taste.

    • Jane's Patisserie
      September 16, 2018 at 3:32 pm

      I completely disagree as I don’t drink coffee at all as I’m really not a fan, and I can’t taste it in this, but that’s up to you. x

  • Katie
    September 11, 2018 at 7:28 am

    Hey! Love you recipes. Can you just confirm the cooking time please. In the intro it says 35 mins and then 50-60 in the instructions? Thank you xx

    • Jane's Patisserie
      September 11, 2018 at 8:29 am

      Ooh it appears it calculated it wrong haha! It’s the 50-60. x

    • Katie
      September 11, 2018 at 5:52 pm

      Fab! I have a dodgey oven anyway so will take as long as it takes haha. Will make sure to tag you on Instagram! Thank you

    • Jane's Patisserie
      September 11, 2018 at 9:27 pm

      Hahaha mine used to be so I know what you mean!! Enjoy!

  • Kerry Hanson
    September 7, 2018 at 11:26 am

    Does this recipe really use 500g of sugar or is it a misprint? It seems rather a lot.

    • Jane's Patisserie
      September 7, 2018 at 3:38 pm

      500g is correct. As you get so many slices from it, it’s not that much per portion.

    • Kerry
      September 9, 2018 at 9:10 pm

      5 stars
      Thank you. I went ahead and made it and I must say, it’s one of the most delicious chocolate cakes I’ve tasted…….my husband has even requested it instead of an actual cake for his 40th birthday in November! Thank you for sharing your wonderful recipes, I haven’t found one yet that hasn’t been amazing! 😊

    • Jane's Patisserie
      September 9, 2018 at 9:38 pm

      Ahh amazing!!!

    • Sophie Blaine
      December 17, 2018 at 6:35 pm

      How deep was the tin you used?

  • Imogen Bett
    September 2, 2018 at 1:20 pm

    Hi what brand of dark chocolate do you use?

    • Jane's Patisserie
      September 2, 2018 at 2:51 pm

      It can really range, but most often or not its supermarket own basic dark chocolate! X

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