Preheat your oven to 350°F (175°C) and prepare a 9x13 baking dish lined with aluminum foil and sprayed with nonstick cooking spray.

In a stand mixer, cream together the unsalted butter, granulated sugar, and golden brown sugar until fluffy and light in color.

Add the large eggs one at a time mixing well after each addition, then add the pure vanilla extract and mix until combined.

Gradually add the all-purpose flour, baking soda, and salt, mixing just until no flour streaks remain.

Fold in the M&M’s and mini chocolate chips with a spatula, reserving some M&M’s for topping.

Transfer the mixture to the baking dish, smooth the surface, and press the reserved M&M’s on top.

Bake in the preheated oven for 30-35 minutes or until the edges are golden brown.

Allow cooling completely in the pan before lifting out and cutting into squares.