Preheat oven to 350. Prepare a 13 x 23 cm pan with cooking spray and flour; set aside. In a mixing bowl, combine brownie mix, eggs, water, and oil. Stir until well blended. Spread into prepared pan. Bake for 25 minutes or until set. Spread marshmallow creme gently over hot brownies (see notes). Pour melted frosting over marshmallow creme. Swirl with knife to marble. Cool completely.