Chex Muddy Buddies

9 cups Rice or Corn Chex
1 cup semisweet chocolate chips
1/2 cup peanut butter
1/4 cup butter
1 tsp vanilla
1 1/2 cups powdered sugar

Into large bowl, measure cereal; set aside.  In 1 quart bowl, microwave chocolate chips, peanut butter and butter uncovered on High 1 minutes; 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.