Add the cereal to a gallon ziploc bag. Set aside.
Add the chocolate, vegan butter, and peanut butter to a microwave safe bowl. Microwave in 30 second intervals, stirring after each interval, until the chocolate and butter are completely melted and everything is mixed together smoothly.
Pour the chocolate, peanut butter mixture into the bag with the cereal, and seal the bag. Toss around the bag until the cereal is fully coated in the chocolate, and it is evenly distributed.
Whisk together the cocoa powder, coconut milk powder if using, and the powdered sugar. Pour the mixture into the bag, seal it again, and toss once more until the cereal is fully coated in the powder.
Pour the cereal out onto a sheet pan and spread it out to cool and dry for about 10-15 minutes.
Sprinkle the marshmallows over the puppy chow, and sprinkle with the sprinkles. Toss and then store in air-tight containers or bags.