Preheat oven to 350 degrees
Crush or blend the Graham Crackers into crumbs.
In the bowl with a stand mixer, cream together the butter and sugars. Add egg and vanilla and mix well.
Add the graham cracker crumbs, flour, baking powder, and salt. Mix until a crumbly dough forms.
Line a 9x13 inch baking pan with parchment paper. Press 2/3 of the cookie dough into the pan.
Unwrap six Hershey bars and layer them over the cookie dough.
Spoon the marshmallow creme over the chocolate bars and spread it out. Then sprinkle the remaining cookie dough over the marshmallow creme and press down gently.
Bake for 30-35 minutes until edges are browning, top is golden, and marshmallow creme that is visible looks toasty.
Remove from the oven and allow to cool completely, at least four hours, before serving. Use the parchment paper to remove the bars from the pan before slicing.
Store covered at room temperature for up to three days.
