01 -
Line the bottom and two opposite sides of an 8x8-inch baking pan with parchment paper, leaving a 2-inch overhang to create a sling.
02 -
Cut the unsalted butter into 6 pieces and melt in a large pot over medium-low heat. Stir in the creamy peanut butter, vanilla extract, and kosher salt until combined and smooth.
03 -
Add half the mini marshmallows and stir until melted. Add the remaining marshmallows and stir until fully melted, returning to low heat if necessary.
04 -
Fold the rice crisp cereal into the marshmallow mixture until evenly coated. Transfer half the mixture to the prepared baking dish, pressing it into an even layer.
05 -
Arrange the Reese's peanut butter cups in a single layer over the pressed cereal mixture.
06 -
Top the peanut butter cups with the remaining cereal mixture, pressing it gently into an even layer.
07 -
Melt the semi-sweet chocolate chips in a microwave-safe bowl in 30-second increments, stirring between each, until smooth. Alternatively, melt over low heat on the stovetop.
08 -
Pour the melted chocolate over the bars and spread it evenly. Refrigerate for 40 minutes, or until the chocolate is set.
09 -
Use the parchment sling to lift the slab from the baking pan. Transfer to a cutting board and cut into 16 squares.