Combine chocolate chips, butter, and peanut butter in a microwaveable bowl. Microwave for 1 minute on high, then another 30 seconds until you can stir the mixture smooth. Stir in vanilla. Place the Rice Chex cereal into a large bowl, then pour the chocolate mixture over the top of it and mix well.
Pour mixture into a large 2 gallon bag, then add the powdered sugar. Seal the bag and shake until it's coated by the powdered sugar. Open the bag, add in the crushed peppermint and shake again.