1Heat oven to 350°F. Line 9-inch square pan with foil so foil extends about 2 inches over sides of pan. Spray foil with cooking spray. Make and bake brownies as directed on box. Cool completely, about 1 1/2 hours.
2Remove brownies from pan by lifting foil; peel foil from sides of brownies. Using 2 1/2-inch star-shaped cookie cutter, cut brownies. Squeeze frosting on star-shaped brownies. Sprinkle with decors.