M&M Cookie Bars!

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Super Chocolatey Cookie Dough full of M&M’s, making THE Most Delicious M&M Cookie Bars Ever!


I have been after a Cookie Traybake recipe for SO LONG. I have struggled so many times as a majority of the recipes are american, and therefore in ‘Cup’ measurements, and no offence to anyone…  but I hate Cup measurements. I just find them so unreliable and it just doesn’t make sense too me. After a good few hours of Pinterest searching for the  next few months of baking inspiration, I saw some amazing cookie recipes. As I have a good few cookie recipes however, I tried Cookie Bars. Something about these M&M Cookie Bars was just perfect.

I did have to spend plenty of time however googling each weight of ‘cup’ measurement to find out what it was in grams, and when it didn’t entirely make sense I took a random stab at scaling up or down so make it a whole amount, and oh my days THESE ARE SO GOOD. Like, I have tried recipes before and they have utterly failed. I have had to bake some cookie bars in the oven for near enough an hour and a half, and they’ve been disgusting. These ones however, oh my, these ones. They took the correct amount of time to bake, with the random guessings of some ingredients, and they are SO YUMMY.


I think I actually ended up annoying my parents by babbling on all day about how happy I was that these turned out so well. Seriously, every half hour I would say “I’m so proud about how amazing these are” and by the end of the day, my parents were finishing the sentence for me. But seriously, I didn’t know whether the colour of the M&M’s would run or not, but they didn’t. They stayed so bright and colourful, making sure these look perfect. The dark chocolatey style cookie base marries so well with the M&M’s. If you eat the cookie bars when they’re still slightly warm, the M&Ms are gooey, crunchy and amazing.

I changed a few ingredients slightly as I said because I wanted it to suit my style of baking. However, I have never imagined using Cornflour in the cookies, and I honestly think it contributes to how well these baked. I lowered the baking temperature slightly as the first time I made these they were maybe a tad overdone at 20 minutes, and with the temperature 10 degrees lower, they were perfect. I LOVE these bars, and I’m sure you will do too – enjoy!


This recipe makes 16 Cookie Bars!


– 200g Plain Flour
– 50g Cocoa Powder
– 1 tsp Bicarbonate of Soda
– 1/2tsp Salt
– 1tbsp Cornflour
– 115g Unsalted Butter/Stork
– 55g Granulated Sugar
– 135g Light Brown Sugar
– 1 Medium Egg, beaten
– 1/2tsp Vanilla Bean Extract
– 2x 165g Bags Chocolate M&M’s



1) Preheat your oven to 190C/170C Fan and line a 9x9inch Square Tin with parchment paper, and leave to the side for now.

2) Whisk/Mix the Plain Flour, Cocoa Powder, Bicarbonate, Salt and Cornflour together so its evenly distributed – leave to the side.

3) In a larger bowl, melt the butter. Add in the two sugars, and whisk for about 2 minutes so the sugar starts to dissolve and the mixture is smooth. Add in the Egg and the Vanilla, and whisk again briefly till smooth.

4) Add in the Dry Ingredients, the M&Ms (leave back a handful), and mix with a spatula till a thick cookie dough is formed.

5) Press the mixture into the bottom of the tin and press in the handful of into the top for decoration. Bake the traybake in the oven for 18-20 minutes, until the top of the cookie bake looks ‘dry’ and a skewer comes out basically clean, bar a few crumbs.

6) Leave the cookie bake to cool for about 10 minutes, then leave to cool fully on a wire rack. Cut the bake into 4×4 for decent sizes, or 5×5 for smaller ones! Enjoy!


Tips and Ideas

This delicious recipe is based on a recipe by Crunchy Creamy Sweet which I have adapted to grams, and swapped up slightly!

I used oodles of Chocolate M&Ms in this recipe, and the colour on them stayed perfect even after baking, but I’m sure it would work with the Crunchy M&M’s, the Peanut M&M’s, or even smarties for example!

These delicious beings will last in an airtight container for up to 5 days, but honestly, they’ll be eaten before then.

I’ve never personally tried this mix as an actual cookie, but if you try it out, let me know how you get on – I’d love to know if it worked!



Find my other Cookie & Traybake Recipes on my Recipes Page!

You can find me on:

J x

© Jane’s Patisserie. All images & content are copyright protected. Do not use my images without prior permission. If you want to republish this recipe, please re-write the recipe in your own words and credit me, or link back to this post for the recipe.

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!


  • Ellie
    June 28, 2020 at 10:36 am

    Would you use the same amount of ingredients if using a 8inch round cake tin to make it into a giant cookie rather than in bars?

    • Jane's Patisserie
      June 28, 2020 at 5:11 pm

      Yes you can – the depth will increase so the cooking time will also increase x

    • Ellie
      June 28, 2020 at 5:38 pm

      Thank you for the reply Jane.
      How much longer should I increase the time for? I have tried to make giant cookies before and they always come out like cakes, they are far too dense. Is there anyway I can stop this from happening? 🙂

    • Jane's Patisserie
      June 28, 2020 at 7:33 pm

      Have a look at my mini egg cookie cake, or my M&M cookie cake recipe! x

  • Frost clan
    June 3, 2020 at 1:37 pm

    You have fast become one of my fav go to pages for yummy treats that’s taste just like my favourite cafes/bake shops would serve. I’ve done the Caramac fudge and milky bar cheesecake both turned out amazing, the kids have now picked these to try next. Excited to see how they turn out thank you for sharing all your recipes and tips 😊

    • Jane's Patisserie
      June 3, 2020 at 9:31 pm

      Ahh yay!! I hope you and the kids love these too!!

  • Elliott
    May 31, 2020 at 9:22 am

    Im thinking of making these but don’t fancy the chocolate base so was wondering do i just remove the cocoa powder and top up the by that amount?

    • Jane's Patisserie
      May 31, 2020 at 12:26 pm

      Yesss, remove the cocoa and top up the flour!!

  • Kulvinder
    May 18, 2020 at 10:53 am


    Can you substitute self raising flour 1:1 with the plain flour /bicarb mixture?

    • Jane's Patisserie
      May 18, 2020 at 11:05 am

      Hey! So when using self raising instead of plain/bicarb it isn’t a straight swap – they will rise up more and then maybe sink in again, or even have a slightly cakey texture, but otherwise it should be fine!

  • Mads
    May 6, 2020 at 5:52 pm

    Hi Jane, I’m not able to access cornflour so what would be a good substitute?

  • Rachael
    April 13, 2020 at 4:17 am

    I’m about to try these but I only have crispy M&Ms do you think that would be ok ?
    Also I want to try the oreo cookie bake today too but I do ‘t have the cadbury oreo bar just 8 packs of oreos lol do you think I could substitute the cadbury bar for normal oreos half and choc chipc half?

    Thanks! i’ve tried the mini egg bars before and they went down very well 🙂

    • Jane's Patisserie
      April 27, 2020 at 8:35 pm

      Yes definitely they should be fine!! And yeah half oreos and half chocolate chips should be fine!! x

  • Joyce Ribey
    April 19, 2019 at 2:33 am

    I wish these were in metric measurement so we could try them in Canada.

    • Jane's Patisserie
      April 19, 2019 at 8:23 am

      They are in metric?

    • A
      May 13, 2020 at 4:55 am

      Hi Jane!
      If I wanted to bake these in an aluminium foil tray what size tray would you recommend and would the cooking time change? Thank you!

    • Jane's Patisserie
      May 13, 2020 at 8:55 am

      I don’t often bake in foil trays so I’m not sure what sizings are sold – but as close to the actual size is best, and then the timings should be the same!

  • Josephine
    December 16, 2018 at 2:55 pm

    Hi Jane, I love these bars and many of your other recipes! Thank you for sharing as you do. I wondered if these would freeze well? I’d like to make some ahead – I can’t seem to manage to save any for any length of time 😉 xxx

  • Libby
    October 1, 2018 at 2:05 pm

    Oh my goodness these are amazing!!
    I’ve just made them in preparation for a school coffee morning tomorrow, obviously I had to give them a little nibble beforehand and WOW they are delicious, eye look brilliant too so should go down a treat
    This is the second recipe from your blog I’ve tried and both have turned out great so I will certainly be trying more.
    Thank you for sharing x

  • Dan
    June 6, 2018 at 7:38 pm

    Hi Jane
    These were Delicious! Thanks. They went down very well with everyone. I will be making more bars and brownies from your blog in future. Next up… Rolo Cookie Bars

  • Creme Egg Cookie Bars! - Jane's Patisserie
    March 28, 2018 at 2:39 am

    […] Cookie,  along with a looooad of Chocolate to boot. I based this recipe very similarly on my M&M Cookie Bars recipe as its a really good chocolatey recipe. You can easily make these without the extra cocoa […]

  • Fiona
    January 27, 2018 at 9:40 am

    Have been wanting to try some recipes for ages but we live out in the middle east and some brands of chocolate are difficult to find or the imported ones just don’t taste right. M&M’s seem to taste the same wherever they are made.
    We made these today and they were fantastic! Don’t think they will last long!

  • Jo
    August 28, 2017 at 5:44 pm

    Made these last week and they were fabulous!

    I’m planning to make them again with Reese’s Pieces and vegan margarine, so that they’re dairy free. The only downside is that I shall then have to share them with my lactose intolerant husband!

  • Soft & Chewy M&M Cookie Bars
    March 5, 2017 at 8:37 am

    […] additional chocolate in their cookie bars? I spotted this recipe on Pinterest and adapted it from Jane’s Patisserie. Like Jane, I have a few issues when it comes to American recipes as they can be unreliable as she […]

  • Amy
    September 22, 2016 at 10:20 am

    Hi, do you think I could use the same weight of mint aero (either bubbles or normal bar) in this recipe, or would it drastically effect the bake? Thanks!

    • Jane's Patisserie
      September 22, 2016 at 10:23 am

      Ummm I’m not sure if I’m honest – it would affect the bake but I don’t know how badly? Maybe only put in one bar/bag and then some mint extract, and normal chocolate chips?

    • Amy
      September 22, 2016 at 12:56 pm

      Thanks – shall give it a go! Got to experiment sometimes.

    • Jane's Patisserie
      September 22, 2016 at 5:57 pm

      Very true!

  • Meggan
    September 7, 2016 at 11:00 pm

    I made these today for work, it’s R U OK? Day today. I used yellow M&M’s on top and they taste amazing! Although they didn’t turn out as fudge-y as they look in the pictures- mine are more cake-y. Any tips?

    • Jane's Patisserie
      September 7, 2016 at 11:02 pm

      Mine weren’t really fudgey, just more cookie like.. Maybe bake for a bit longer?

    • Meggan
      September 14, 2016 at 7:12 am

      Ok thanks- I’ll give that a try next time!

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