from Chex site
9 cups corn, rice or wheat chex (full box)
1 cup semisweet chocolate chips
1/2 cup peanut butter
1/4 cup butter or margarine
1 teaspoon vanilla
1 1/2 cups powderd sugar
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.