Preheat oven to 375°
Spray a 9X13 baking dish with cooking spray and set aside.
In a stand mixer (or in a bowl with a hand mixer) combine butter, sugars and vanilla until it is well blended.
Add eggs one at a time.
Combine all dry ingredients in a bowl and add to the wet ingredients slowly.
When well combined, gently mix in the chocolate chips and M&Ms.
Pour batter into the baking dish and add extra M&Ms if you see fit.
Bake for 25-30 minutes or until golden. Let it cool and cut into pieces.