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.



  1. 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

  2. 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

  3. 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

  4. 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!

  5. 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!

  6. 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!

  7. 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?

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