1/2 cup unsalted butter, room temperature
1/4 cup brown sugar
1/2 cup granulated sugar
1 large egg, room temperature
1 tsp vanilla extract
1 1/3 cups all-purpose flour
3/4 cup graham cracker crumbs (about 8 graham crackers)
1 teaspoon baking powder
1/4 teaspoon salt
2 king-sized milk chocolate bars
1 1/2 cups marshmallow Fluff (not melted marshmallows because they harden when they cool)
Preheat oven to 350 degrees F. Grease and/or line an 8-inch square baking pan.
In a large bowl, cream together butter and sugar until light. Beat in egg and vanilla.
In a small bowl, whisk together flour, graham cracker crumbs, baking powder and salt. Add to butter mixture and mix at a low speed until combined. Divide dough in half and press half of dough into an even layer on the bottom of the prepared pan. Don’t worry if it seems thin; the baking powder will allow it to rise.
Place chocolate bars over dough (don’t layer the bars, just break them to fit if you need to), then spread the marshmallow Fluff over the chocolate bars. Finally, top the Fluff with the remaining dough by forming the dough into sheets with the palm of your hands and laying it down (as shown above). Don’t worry if the dough isn’t covering everything! It’ll spread out as it bakes.
Bake for 30 to 35 minutes, until lightly browned. If the top is browning too quickly, you can always cover it with tin foil for the remaining baking time. Cool completely before cutting into bars. If you don’t allow them to cool completely, they will crumble when you try to cut them. Makes 16-20 bars.