Melt the chocolate chips and peanut butter in a microwave-safe bowl. Heat in 30-second increments, stirring in between, until creamy and smooth—about 1-2 minutes.

Stir in the peppermint extract to the melted mixture until fully combined.

Pour the chocolate mixture over the Chex cereal in a large bowl, ensuring every piece is coated. Gently stir until evenly covered.

Transfer the coated cereal to a large resealable bag or another bowl.

Add the powdered sugar to the bag or bowl, securely close the bag or stir in the bowl. Shake or stir until well-coated.

Mix in the mint chocolate candies, gently fold them into the puppy chow.

Spread the coated mixture on a baking sheet lined with parchment paper to cool. Let it sit for about 10 minutes.