Line a half sheet rimmed baking tray with parchment, wax paper, or a silicone mat. Set aside.

Add the chocolate, peanut butter, and butter to a large metal bowl. Sit bowl over a pan of simmering water to create a bain-marie, or double boiler.

Melt, stirring gently with a whisk, until smooth and completely melted. Stir in the vanilla extract.

Remove from heat. With a rubber spatula or wooden spoon, gently stir the cereal into the melted chocolate.

Scoop about 3/4 of the confectioner’s sugar into a large plastic food storage bag.

Add the chocolate-coated cereal, then seal the bag and shake vigorously to coat. Add the remaining sugar and shake again.

Spread coated cereal on prepared baking tray. Set aside to cool at room temperature, about 30 minutes, or until set.

Serve immediately, or store in an airtight container at room temperature for up to 1 week.