In a large microwave-safe bowl, combine the butter, peanut butter, and chocolate chips.

Microwave in 30-second intervals, stirring between each, until the mixture is melted and smooth (about 1–2 minutes).

In a large bowl, gently mix the Rice Chex and pretzel sticks.

Pour the melted chocolate mixture over the cereal and pretzels.

Use a spatula to gently stir until everything is evenly coated.

Transfer the coated mix to a large resealable plastic bag and add the powdered sugar.

Seal the bag and shake until all pieces are coated with powdered sugar.

Spread the mixture on a baking sheet lined with parchment paper and let it cool for 15–20 minutes.

Once cool, stir in the M&Ms and serve or store.