In a microwave-safe bowl, combine the chocolate chips, peanut butter, and butter. Melt the mixture on high for about 1 minute, stirring every 15 seconds until it’s smooth.

Pour the Chex cereal into a large mixing bowl. Drizzle the melted chocolate-peanut butter mixture over the cereal, stirring gently to coat.

Add the powdered sugar and cover the bowl, shaking gently until the sugar coats the Puppy Chow evenly.

Fold in the red and blue M&M’s, mixing carefully to avoid crushing the candies.

Spread the Puppy Chow onto a baking sheet in a single layer and let cool completely before serving.