Measure out the Rice Chex cereal into a large bowl.
In a microwave-safe bowl, combine the chocolate chips, peanut butter, and butter.
Microwave the mixture on high for 30 seconds, then stir.
Continue microwaving in 15-second intervals until melted and smooth.
Add the vanilla extract to the melted mixture and stir well.
Pour the chocolate mixture over the Rice Chex cereal.
Gently fold the cereal to coat it evenly.
Transfer the coated cereal into a large resealable bag.
Add the powdered sugar to the bag and shake until well coated.
Spread the Puppy Chow on a baking sheet to cool before serving.