Into large bowl, measure cereal; set aside.

In 1-quart microwavable bowl, microwave chocolate chips, peanut butter and butter uncovered on High 1 minute; stir.

Microwave about 30 seconds 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.