Preheat the oven to 350°F. Spray a 13x9x2 inch baking pan with gluten-free, non-stick cooking spray.
Melt 4 tbsp of the butter. In a mixing bowl, combine the graham style crumbs with ¼ c sugar and the melted butter. Pat firmly into the prepared baking dish covering the bottom with an even layer. Bake for 10 minutes. Leave the oven on.
In a medium mixing bowl, whisk together the gluten-free flour blend, baking powder, salt and instant espresso, set aside.
Measure ½ c of the chocolate chips and set aside. Combine the rest of the chips with the remaining 1 c butter and microwave for 3-3½ minutes or until melted. Stir the chocolate and butter together until fully melted and glossy. Stir in the remaining 1 c of sugar then the eggs, flour mixture and vanilla. Pour the batter over the graham crust and bake for 20 minutes. Leave oven on.
Top the brownie layer evenly with the reserved ½ c of chocolate chips, the chopped walnuts or pecans, drained cherries and the marshmallows. Return to the oven and cook for 5-7 minutes or until a toothpick inserted in the center comes out almost clean. Broil for about 30 seconds to brown the marshmallows – watch carefully so they don't burn.
Let the brownies cool. Cut into squares.