Preheat your oven to 350°F (175°C) and line a 9x13-inch baking pan with aluminum foil, lightly spraying with nonstick cooking spray.

In a medium bowl, whisk together the all-purpose flour, graham cracker crumbs, baking powder, and salt.

In a large mixing bowl, beat together the unsalted butter and light brown sugar until light and fluffy. Add in the beaten eggs and mix well.

Gradually add the dry ingredients to the wet mixture, mixing on low speed until just combined.

Press half of the dough evenly into the prepared baking pan to form the crust.

Spread the marshmallow topping evenly over the crust and sprinkle with milk chocolate chips.

Crumble the remaining dough over the marshmallow and chocolate layers, leaving some exposed.

Bake for 30 to 35 minutes, or until the top is golden brown and the center is soft.

Remove from the oven and let cool completely in the pan. Lift out using the foil and slice into squares.