Preheat the oven to 350 degrees F. Grease a 9x13'' baking dish or line with parchment paper.

In a medium bowl combine the flour, graham cracker crumbs, baking powder and salt.

In a separate large bowl, cream the butter and sugar together until light and fluffy, about 2 minutes.

Add the eggs and vanilla and beat until well combined. Reduce the mixer speed to low and add the flour mixture, mixing until combined.

Press half of the dough mixture evenly into the bottom of the prepared pan.

Dollop marshmallow creme on top and gently spread into an even layer. If the marshmallow creme gets really sticky you can dip your spoon in hot water (shake off excess water) and it will help to spread.

Break the chocolate bars into pieces and layer over the marshmallow (or sprinkle with chocolate chips). Place small pieces of dough all over the top, flattening into an even layer as best you can.

Bake for 28-32 minutes or until golden brown. Allow to cool completely before cutting and serving.