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

4.89 from 9 votes
Chocolate Sheet Cake!
Prep Time
15 mins
Cook Time
55 mins
Total Time
50 mins

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

Course: Cake
Cuisine: Traybakes
Keyword: Chocolate
Servings: 20 Servings
Calories: 472 kcal
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
  1. Preheat your oven to 160/140C Fan, and line a 9x13" Tin with parchment paper. 

  2. In a heatproof bowl, microwave the Dark Chocolate & Butter till melted – mine takes two minutes! 

  3. Pour the Coffee Granules into 125ml Boiling Water and mix – add the coffee to the Chocolate/Butter mix and stir well till smooth!

  4. 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!

  5. 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. 

  6. 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
  1. With an electric mixer with the paddle attachment, beat the butter until its very smooth and supple (couple of minutes)

  2. 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.

  3. 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!

Recipe Notes
  • 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%
* Percent Daily Values are based on a 2000 calorie diet.


Find my other Recipes on my Recipes Page!

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J x

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  1. 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

  2. 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?

  3. 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 😁

  4. 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

  5. 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

    1. 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!

  6. 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.

  7. 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!

  8. 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

  9. 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 😞

    1. 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!

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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

    1. 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

    1. 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! 😊

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