1. Preheat the oven to 350 degrees. Line a square baking dish with parchment paper.
2. Beat the butter and sugar until fluffy. Add the egg and vanilla and mix well. Add the flour, baking powder, and salt. Stir in the graham cracker crumbs.
3. Press 2/3 of the dough into the bottom of the baking dish. Press the chocolate bars on top of the dough. They should make an even layer in an 8×8 pan. 4. Melt the peanut butter for about 30 seconds in the microwave and drizzle it over the chocolate bars.
5. Spread the marshmallow cream over the chocolate and peanut butter.
6. Roll the remaining 1/3 dough onto the chocolate foil wrappers (or some other nonstick surface). When you’ve made an even square, gently peel it off and press it on top of the marshmallow cream.
7. Bake for 25 minutes or until golden brown on top. Let cool for best serving results (see notes).