Line two baking sheets with parchment paper and set aside. Pour the cereal into a large mixing bowl.
In a microwave-safe bowl, combine the vegan chocolate chips, peanut butter, and vegan butter. Microwave in 30-second intervals, stirring between each, until smooth and fully melted.
Pour the melted chocolate mixture over the cereal and use a rubber spatula to gently stir until every piece is evenly coated.
Add 1 cup of powdered sugar to a large zip-top bag, then ⅓ of the chocolate-coated cereal. Add 1 cup more powdered sugar, half of the remaining cereal, the last cup of powdered sugar, and the rest of the cereal. Seal the bag and shake until everything is evenly coated.
Spread the coated cereal onto the prepared baking sheets and let cool for about 10 minutes.
Store your vegan puppy chow (muddy buddies) in an airtight container or resealable bag at room temperature for up to 5 days, or freeze for up to 6 months.