Measure cereal into large bowl; set aside. In 1-qt. microwaveable bowl, microwave chocolate chips, peanut butter and butter uncovered on high for one minute; stir. Microwave about 30 seconds or longer or until mixture can be stirred smooth; stir in vanilla. Pour mixture over cereal, stirring until evenly coated. Pour into 2-gallon resealable food storage plastic bag. Add powdered sugar. Seal bag. Shake until well coated. Spread on waxed paper to cool. Store in airtight container in refrigerator.