Grease a 12-inch pizza pan. Prepare brownie mix according to package directions.
Carefully spread batter into prepared pan. Bake in a 350 degree F oven for 15 minutes or until edges are set. Spread a layer of Nutella over the top of your partially baked brownies, then sprinkle with toppings. Return to oven. Bake 8 minutes more or until a wooden toothpick inserted near the center comes out clean. Toast marshmallows under broiler for 2 minutes, if desired. Cool on a wire rack. To serve, cut into wedges. Makes 16 servings.