Preheat the oven to 350 F. Grease an 8x8 or 9x9 inch pan with nonstick spray, or line with parchment paper. Set aside.
In a large bowl or stand mixer, beat together butter and 1/4 cup peanut butter. Add the brown sugar and white sugar and beat again.
Mix in the egg and vanilla; beat thoroughly.
Dump the flour on top but do not stir. Add the graham cracker crumbs without stirring. Use a small spoon to add the baking powder and salt to the top of the flour. Stir it gently with the flour. Then use the beaters to mix in the dry ingredients, only mixing until barely combined.
Spread about half of the dough into the bottom of the prepared pan. Get your finger tips wet it you have issues spreading.
Spread 1/3 cup of peanut butter over the top of the dough.
Sprinkle with all of the chocolate chips.
Remove the lid and all foil from the top of the marshmallow cream. Microwave for about 20 seconds. Watch it. When the marshmallow cream rises above the lip of the container, take it out. (Warming it makes it so much easier to spread.) Spread all of the marshmallow cream over the chocolate chips.*
Use your hands to shape pieces of the remaining dough into about 4 or 5 flattened shingles. Add them on top of the marshmallow cream, filling in gaps as you go. It doesn't need to be perfect, just try to cover the whole thing with dough. It's easier for me than spreading.
Bake at 350 F for 28-30 minutes, until lightly golden on top.
Let cool (maybe. I mean, if you want.) Cut and serve! With lots of milk. Trust me.