Heat oven to 350 degrees. In an 8x8 pan spray the sides with non-stick cooking spray.
In a food processor, pulse the graham crackers until fine. In a small bowl, combine the crumbs, 2 Tbs sugar, and 1/4 cup melted butter. Press firmly in the bottom of the 8x8 dish.
In a medium bowl or kitchenaid mixer, combine softened butter, 1 cup sugar, and cocoa until smooth. Add eggs and stir. Add flour, vanilla and salt until the mixture is combined. Spread half over the graham cracker crust.
Sprinkle marshmallows on top of half of the layer, then spread remaining batter on the top. Bake at 350 for 25 minutes.
Sprinkle the chocolate chips or broken hershey bars on top of the brownie. Return to the oven and let cook for 3 more minutes. Remove from oven and spread chocolate with a rubber spatula. Cool completely.