PREP: Preheat oven to 350 degrees F. Lightly grease or spray a 9-inch cast iron skillet or 9- inch cake pan. Set aside.
CREAM BUTTER and SUGARS: In a medium-sized bowl, cream room-temperature butter (Note 1), white sugar, and brown sugar for about 2-3 minutes. Add in egg and vanilla. Mix until combined.
DRYINGREDIENTS & COMBINE: In a separate bowl, stir together flour (See Note 2), baking soda, baking powder, and salt. Add dry ingredients to the wet and mix until a dough forms. Do not over mix.
DIVIDE DOUGH: Divide the dough in half. Press one half into the bottom of the skillet or cake pan and layer halved Reese's cups on top.
REMAININGDOUGH: To the remaining cookie dough, add in the milk chocolate chips and peanut butter M&M's. Stir to combine and then press that remaining cookie dough on top of the Reese's cups and smooth the dough into 1 even layer. The Reese's cups should be covered with dough.
BAKE: Bake for 20-25 minutes until the edges are light golden brown, keeping the center slightly soft for a perfect Pizookie.
SERVE: Serve immediately with ice cream and hot fudge if desired.
Notes
Note 1: Butter: Use room temperature butter. If it’s too soft or melted, the edges may burn before the center bakes properly.Note 2: Measuring flour:When measuring flour for this recipe, spoon and level it. Pressing the measuring cup into the flour container can lead to using too much.