Step 1

Preheat the oven to 350° F. and grease a 9-inch cake pan (or tart pan) with baking spray. Set aside.

Step 2

In a medium bowl mix the flour, baking soda, and salt using a fork or wire whisk to combine. Set aside.

Step 3

In a large mixing bowl add the butter, peanut butter, sugars, egg, and vanilla extract. Cream together with an electric mixer on medium speed until well combined (about 4 minutes). Use a spatula to scrape down the sides halfway through mixing.

Step 4

Add the dry ingredients to the wet ingredients. Mix on low speed for 10 seconds then increase speed to medium and mix just until combined.

Step 5

Fold in  ½ cup of M&M’s and the peanut butter chips using a rubber spatula.

Step 6

Transfer the cookie dough to the pan. Use your hands to press the dough out evenly until flat.

Step 7

Press ¼ cup of M&M’s into the top of the cake.

Step 8

Bake for 16-20 minutes or until the edges of the cookie are just starting to turn golden brown. Do not over bake, you want the cookie to be soft in the center. Remove cookie from oven and cool about 10 minutes on a wire rack, then run a knife around the edges of the pan to loosen cookie and invert onto rack to finish cooling completely before frosting.

Step 9

Once cooled frost the cake to your liking. You can drizzle icing or use store-bought or homemade frosting to pipe onto the cookie cake.

Step 10

Sprinkle the remainder of the M&M’s onto the frosting.