Preheat oven to 350°F and spray a 9″ pie pan with baking spray.
Beat butter and sugar in a large bowl, then add the egg and vanilla and mix.
Stir in flour, graham cracker crumbs, and baking powder.
Press 2/3 of the dough onto the bottom and sides of the pie pan.
Spread marshmallow creme over the crust, then top with chocolate squares.
Sprinkle 1 cup of marshmallows on top.
Flatten the remaining dough into disks and cover the marshmallows, leaving some exposed.
Sprinkle a few more marshmallows on top.
Bake for 15-20 minutes or until golden brown, then cool before adding the remaining chocolate squares and serving.