In a large mixing bowl, measure out the crispy rice cereal.
In a saucepan over medium heat, melt the chocolate chips, peanut butter, and butter, stirring until smooth.
Remove the saucepan from heat and stir in the vanilla extract.
Pour the chocolate mixture over the crispy rice cereal, gently folding until all the cereal is coated.
In a large paper bag or a clean, sealable plastic bag, add the powdered sugar.
Transfer the chocolate-coated cereal into the bag, seal it, and shake vigorously until the cereal is fully coated with powdered sugar.
Spread the Puppy Chow on a parchment-lined baking sheet to cool and set.
Once cooled, store the Puppy Chow in an airtight container.