How to Make It
Line a rimmed baking sheet with parchment paper. Combine peanut butter, butter, and 1 1½ cups of the chocolate chips in a very large microwave-safe bowl. Microwave on high, stirring every 30 seconds, until melted and smooth, about 1½ minutes. Add the Lucky Charms to the bowl and toss until coated.
Transfer the cereal mixture to the prepared baking sheet and spread to the edges. Let cool completely, about 30 minutes.
Dust with the powdered sugar and toss until well-coated. Add the Sno Caps and M&M's and toss to combine. Melt remaining 1/2 cup chocolate chips and drizzle overtop. Top with sprinkles.