1Heat oven to 375°F. Spray 13x9-inch baking pan with cooking spray. In large bowl, stir cookie mix, 1/2 cup butter and egg until soft dough forms. Press dough in bottom of pan. Bake 10 to 12 minutes or until edges are light golden brown. Cool 15 minutes.
2In large microwavable bowl, microwave chocolate chips and the remaining 1/2 cup butter on High about 1 1/2 minutes, stirring after 1 minute, until melted and smooth. Add peanut butter; mix until well blended.
3Place cereal in 1-gallon resealable food-storage plastic bag. Using your hands, gently break cereal into small pieces. Gently stir cereal into chocolate mixture until cereal is coated. Spread cereal mixture evenly over cookie crust; gently press. Sprinkle with powdered sugar. Refrigerate about 1 hour or until bars are set. For bars, cut into 6 rows by 6 rows. Store covered at room temperature.