Grease your cake tin and leave to one side. Preheat your oven to 180C (160F).
Mix together your brown sugar and unsalted butter until they arecombined.
Add in the Vanilla, Flour Egg and Cornflour and mix again untilall the ingredients are combined.
Fold through the chocolate chips and M&Ms. Until they are all evenly distributed throughout the mixture.
Pop the mixture into your cake tin and bake in the oven for25-30 minutes. You will know it is ready when the top of the cookies look dry and it doesn’t wobble.
Remove from the cookie and leave to cool completely.