Break apart the chocolate bar and cut up the peanut butter cups and place on a plate and stick in the freezer.

Heat oven to 350 degrees F. Line an 8-inch square baking pan with parchment paper.

Mix melted butter and graham cracker crust together in a small bowl. Add the graham cracker crust to the prepared baking dish. Using your fingers, flatten the crumbs so it’s evenly distributed throughout the pan.

In a small bowl, mix together flour, baking soda and salt. Set aside. Add butter and sugars to a large mixing bowl. Cream together with an electric hand mixer or rubber spatula. Add egg and vanilla extract and mix together. Add flour mixture in two batches, mixing with a rubber spatula and being careful not to overtax. Add chocolate chips and marshmallows and fold in.

Spoon the cookie dough over the graham cracker crust. Spray an offset spatula with nonstick baking spray and use the spatula to smooth the cookie over the graham cracker crust.

Bake for 25 to 30 minutes in a 350 degree F oven, until the cookie dough is mostly set (it’s okay if it’s a little underdone). Remove the baking pan and add 1/4 cup of mini marshmallows on top and return to the oven to bake another 3 to 5 minutes, until marshmallows have melted a little, losing their shape.

Remove baking pan and place on a cooling rack and allow to cool for at least 60 minutes. Take chocolates from the freezer and carefully place them on top around the marshmallows.

Remove bars from baking pan by using the overhang from the parchment paper. Cut into bars when it’s completely cooled. (I even wait to cut them the next day.)