In a very large bowl, add 4-1/2 cups Peanut Butter Captain Crunch and 4-1/2 cups Cap'n Crunch (regular, no berries). Set the bowl aside.

In a separate large, microwave-safe bowl, combine 1/2 cup creamy peanut butter, 1 cup chocolate chips, and 4 tablespoons unsalted butter.

Microwave the mixture in 15-second intervals, stirring well between each interval, until the mixture is fully melted and smooth. Use a spatula to scrape the sides and bottom so everything is incorporated.

Stir in 1/4 teaspoon salt and 1 teaspoon vanilla extract (optional) until combined. If the mixture is very hot, let it sit 30–60 seconds so it’s easier to work with.

Pour the melted chocolate–peanut butter mixture over the two cereals. Use a spatula to gently fold and stir until the cereal is evenly coated, taking care not to crush the cereal. (If you want optional mix-ins to stick to the cereal, fold them in now.)

Divide the coated cereal mixture into two equal portions.

For the first portion: put 1/2 cup powdered sugar into a large resealable plastic bag, add half the coated cereal, then add another 1/2 cup powdered sugar. Seal the bag and shake until the cereal is evenly coated with powdered sugar. Pour the coated cereal into a large clean bowl.

Repeat step 7 with the remaining coated cereal and the remaining powdered sugar (1/2 cup powdered sugar + remaining cereal + 1/2 cup powdered sugar in a bag). Pour this second coated portion into the same large bowl.

If you did not add optional mix-ins earlier, add them now and gently stir to distribute. Let the puppy chow cool if still warm, then store in an airtight container.