1Heat oven to 350?F. Spray 2 (8-inch) round cake pans with cooking spray; line with cooking parchment paper. Make brownies as directed on box, using water oil and eggs. Divide batter evenly between pans.
2Bake 15 to 18 minutes or until toothpick inserted 2 inches from side of pan comes out almost clean. Cool completely in pans on cooling racks. Use parchment paper to lift out of pan. With 2 1/4-inch round cookie cutter, cut out 6 rounds from each brownie. Place 8 of the rounds on cookie sheet; set remaining 4 rounds aside.
3In 2-quart saucepan, heat chocolate chips and peanut butter until melted. Remove from heat; stir in cereal until coated. Spread thin layer of cereal mixture over 8 brownie rounds on cookie sheet. Freeze 15 minutes.
4Remove brownies from freezer. Top each with small scoop of ice cream; stack 1 brownie round on top of another. Top each stack with 1 plain brownie round; press gently. (Clean up sides of cakes with knife, if necessary.) Top with dollop of hot fudge topping. Garnish with candy half.