Preheat oven to 350 degrees F.
Line 8x8" baking dish with aluminum foil and spray with non-stick cooking spray.
Set aside.
In medium bowl, combine flour, graham cracker crumbs, baking powder, and salt.
In separate bowl, beat together the butter and sugar with electric mixer until light and fluffy, about 3 minutes.
Add the egg and vanilla and beat to combine.
Add the dry ingredients gradually, beating just until the dough comes together.
Transfer just a little more than half of the dough to the prepared pan, reserving the rest for the topping.
Gently press the dough into an even layer over the bottom of the pan.
Top the crust with candy bars to create a single layer.
You will probably have to break them up to fit.
Spread the marshmallow creme over the chocolate.
Top with reserved dough and press lightly to create even layer.
Bake bars for 25-30 minutes, or until the topping is golden brown. Let cool completely in pan. Then lift the bars out of the pan and cut into squares. Enjoy!