Yes, this snack is really for people!
Pour your cereal into a LARGE bowl and set aside.
In a one-quart bowl, microwave the chocolate chips, peanut butter, and butter on high for about 1 minute. Stir. Everything probably isn’t melted yet, so continue to microwave in 30 second increments, stirring after each time. When the mixture is smooth and melted, put in the vanilla. Pour this mixture over the Chex cereal, stirring until everything is well coated. Using a 1 or 2-gallon food-storage bag, pour in your coated cereal, leaving room to shake. Add powdered sugar according to how much cereal you have in the bag. (half of the cereal, then use half of the powdered sugar.) Shake until well coated. Spread out on waxed paper to cool. You want to get your coating done quickly so the chocolate is still sticky. Store in an airtight container.