Preheat oven to 350 degrees F. and line 9 x 13 inch baking dish with parchment paper.
Press peanut butter cookie dough layer into baking dish. Use whatever peanut butter cookie dough recipe you’d like. Place cake mix, butter and egg into a large bowl. Mix until dough consistency forms. Press over peanut butter cookie layer. Top with marshmallows and chocolate chips.
Bake for 35-40 minutes until baked through. Let cool completely then cut into bars and serve room temperature.
Notes
Prepare Cookie Dough Ahead of Time. If you can make your peanut butter cookie dough ahead of time, you'll find this will save lots of time the day you plan to bake the recipe.
Use Store Bought Cookie Dough If Needed. If you don't feel like making your own cookie dough, you can run up to the grocery store and get some store bought peanut butter cookie dough that will work just fine too.
Use A Plastic Knife. You will find that by using a plastic knife to cut your bars into squares, it prevents sticking.