Step 1

Heat oven to 325°F.

Step 2

Line 13x9-inch pan with foil, with ends of foil extending over sides. Spray with cooking spray.

Step 3

Mix frosting and powdered sugar in medium bowl until blended. Add food colorings; stir gently just until frosting is streaked with red and yellow colors. Spoon into pastry bag fitted with star tip. Refrigerate until ready to use.

Step 4

Microwave chocolate and butter in large microwaveable bowl on HIGH 2 min. or until butter is melted. Stir until chocolate is completely melted and mixture is well blended. Stir in granulated sugar, then eggs. Add flour; mix well. Pour into prepared pan.

Step 5

Bake 30 to 35 min. or until toothpick inserted in center comes out with fudgy crumbs. (Do not overbake.) Cool completely. Use foil handles to remove brownie from pan before cutting into 24 pieces.

Step 6

Pipe frosting onto brownies. Insert pretzel sticks into brownies to resemble campfires as shown in photo. Thread 2 marshmallows onto each of 24 wooden toothpicks; place on brownies as shown in photo.