Melt the Base: Melt the semi-sweet chocolate chips, creamy peanut butter, and salted butter together in a microwave-safe bowl in short bursts, stirring until completely smooth.
Add Vanilla: Stir the pure vanilla extract right into the warm chocolate and peanut butter mixture.
Coat the Cereal: Pour that warm, glossy mixture right over the Rice Chex cereal in a large bowl. Gently toss everything until every single piece of cereal is completely coated.
Dust with Sugar: Transfer the coated cereal into a large zip-top bag with the powdered sugar. Seal it up and shake until the cereal is well dusted and white.
Add the Crunch: Gently fold in the chopped fun-size Butterfinger candy bars so they mix right in with the sugary clusters without breaking down too much.
Cool and Serve: Spread the mixture out on a baking sheet to cool completely, then dive right in.