Preheat your oven to 350
Line a baking sheet with parchment and then butter the parchment and sides of the pan.
In the bowl of an electric stand mixer add the butter and sugars.
1 cup butter, 1 ½ cup brown sugar, ½ cup white sugar
Mix with a paddle attachment until well blended and light and fluffy.
Add in vanilla and eggs, continue mixing until well incorporated.
2 tsp. vanilla extract, 3 eggs
In a separate bowl combine flour, baking powder, baking soda, and salt, whisk until well incorporated.
3 cups flour, 1 tsp baking powder, 1 tsp baking soda, 1 tsp salt
Add dry ingredients gradually into the mixer, mixing after each addition.
Add in chocolate chips and one cup of the M&M’s fold in until evenly mixed.
2 cups chocolate chips, 2 cups M&Ms
Spread the dough evenly into your prepared pan.
Sprinkle 1 cup of M&M’s across the top of the cookie dough.
Bake for 20-25 minutes or until golden brown.
Allow to cool completely before cutting into 24 squares.
Store in an airtight container