Preheat your oven to 180 C / Gas 4 and line your tray with baking parchment.
Mix the sugars and the butter together (don't worry if the mixture is not creamy, the egg will do the trick!). Add the beaten egg and the vanilla extract and mix well.
Sieve the flour and the baking powder into the creamed mixture and mix well; make sure that none of the flour is left on the edges of the bowl.
Add the M&M's®. At this point you should be able to make a ball with out it being too sticky, if it is sticky add a few teaspoons of flour. Roll out a ball the size of a walnut and place evenly on the baking tray, with six balls on each tray.
Bake in the oven for 10 to 12 minutes. When you take the delicious cookies out of the oven, place then on a cooling rack to cool for 10 minutes. Enjoy!