First preheat your oven to 350 and line a rimed cookie sheet with parchment paper. Butter the entire surface of the parchment and sides of the baking sheet.

Next, in a large bowl, with an electric mixer,  or in the bowl of a stand mixer, cream butter, brown sugar, and white sugar together until light and fluffy.

Next add in the vanilla and eggs, continue mixing on medium speed until the eggs are well incorporated.

In a separate bowl whisk together flour, baking powder, baking soda, and salt until well combined.

Add half the flour mixture to the butter mixture and mix until well incorporated. Add the remaining dry ingredients and continue mixing until all ingredients are well blended.

Add in chocolate chips and one cup of M&M’s fold in using a spatula or wooden spoon until evenly distributed throughout the cookie dough.

Transfer dough into your prepared baking pan and spread it evenly making sure to get it an even thickness. Sprinkle the remaining 1 cup of M&M’s across the top.

Place in oven and bake for 20-25 minutes or until golden brown and the center is completely set. The edges will be a deeper golden than the middle. Your cooking time may vary depending on your pan, and oven so watch the cookies closely. 

Allow to cool in the pan on a cooling rack for at least 30 minutes before cutting into squares.