In a large mixing bowl, add the melted butter and both sugars. Using a balloon whisk, mix to form a smooth paste
Add the egg and vanilla extract and whisk until the mix is thick and smooth
Place a sieve over the bowl. Pour in the flour, bicarbonate of soda, and salt. Sift these into the mix, then gently fold them in until just a few streaks of flour remain
Fold in your M&M’s and chocolate chips. There should be no streaks of flour remaining at this point
Cover the bowl with cling film and refrigerate for at least 30 minutes
Using a small cookie scoop, scoop up about 1 tbsp of the dough and place on a cookie tray about 4 inches apart. I baked mine in batches of 6
Bake in the oven for 8-10 minutes or until the edges are crisp and golden brown
The cookies will look puffy when they come out of the oven, but will flatten and crinkle once cool
Leave them to cool on the tray for about 20 minutes before transferring them to a cooling rack. Enjoy!
Notes
These cookies will last around 3-4 days in an airtight container at room temperature
Leave them to cool fully before serving otherwise they’re likely to fall apart.
Use real butter! Butter substitutes generally do not set hard enough for these cookies
Chill the dough overnight for a more caramelised flavour.
You can freeze the dough balls and cook from frozen. Just make sure no moisture enters the dough whilst in the freezer. They may also need a few extra minutes cooking.