Step 1

Line a baking sheet with parchment paper. Combine the chocolate chips, peanut butter chips and shortening in a large heatproof bowl set over a saucepan of simmering water (do not let the bowl touch the water). Stir until melted and smooth, 2 to 4 minutes. Remove the bowl from the pan and add the cereal and peanuts. Stir with a rubber spatula until evenly coated.

Step 2

Spoon the cereal mixture into clusters (about 2 tablespoons each) onto the prepared baking sheet; sprinkle with nonpareils. Refrigerate until firm, about 30 minutes.