Add Rice Chex, Corn Chex, pretzels, and nuts into a large mixing bowl. Gently toss until evenly combined, making sure the mix is spread out for easy coating later.

Place white chocolate chips in a microwave-safe bowl. Heat in 20 to 30 second intervals, stirring after each interval until fully melted and smooth. Stir in coconut oil if needed to thin the chocolate.

Slowly pour the melted white chocolate over the cereal mixture, moving your hand around the bowl to distribute it as evenly as possible.

Use a spatula to gently fold and mix the ingredients until most pieces are coated. Avoid mixing too fast to prevent breaking the cereal.

Sprinkle powdered sugar over the warm mixture. Toss gently until all pieces are lightly coated and no longer sticky. Add more sugar if needed.

Spread the mixture onto a parchment-lined baking tray in an even layer. Let it sit at room temperature for 20 to 30 minutes, or until the chocolate is fully set.

Break the mix into clusters and transfer to an airtight container for storage.