Cream together the butter, brown sugar and white sugar until its smooth. Mix egg and vanilla extract in until incorporated. Don’t overmix. Eggs are finicky lil buggers. Add flour, (salt if needed), graham cracker crumbs and baking powder and mix until evenly incorporated Press half of the dough into the bottom of a greased/lined 8×8 pan. Set up a layer of chocolate =) I didn’t anticipate having that empty space in the corner cause I thought it was a huge chocolate bar, but luckily I had a spare Aero bar kicking around. Random, but convenient. Spread the marshmallow Fluff on top of the chocolate. Gently press the remaining dough on top of the bars. Bake for 30 minutes until it’s lightly goldened and delicious looking. Let cool on a wire rack until completely cool. If you don’t way the fluff will both burn you and ooze everywhere. You have been warned.