1. In a microwave-safe bowl, combine chocolate chips, peanut butter, and butter. Microwave on high for 1 minute, then stir until smooth. If needed, microwave for an additional 30 seconds.
2. Stir in vanilla extract.
3. Pour the chocolate mixture over the Chex cereal in a large mixing bowl. Stir gently until the cereal is evenly coated.
4. Transfer the coated cereal into a large Ziploc bag. Add the powdered sugar, seal the bag, and shake until the cereal is well coated.
5. Spread the mixture out on a baking sheet to cool. Store in an airtight container.
Notes:
For a fun twist, add some M&Ms or other candies to the mix after coating with powdered sugar.