Preheat oven to 325°F and line a 9"x13" baking pan with parchment paper or foil, leaving some paper hanging over the sides.

Crush graham crackers, then combine ½ cup melted butter with crumbs and stir until well combined. Pour mixture into prepared pan and press evenly into the bottom. Freeze while making the cookie dough.

In a large mixer, blend together both sugars and the melted butter. Add eggs one at a time and vanilla, blending until well combined.

In a separate bowl, whisk together flour, baking powder, and salt. With the mixer on low, slowly add the flour to the butter/sugar mixture and stop when all the flour is added. Fold in the marshmallows and chocolate chips until well combined.

Retrieve the baking pan from the freezer and scoop the dough on top of the prepared crust, spreading evenly with an offset spatula.

Top the dough with the Hershey bars, graham cracker pieces, and mini marshmallows, pressing them into the dough slightly.

Bake for 35-45 minutes, until the top is golden brown and there is no wet batter visible.

Remove from oven and allow to cool completely before cutting.