01 -
Line a 9x13-inch baking pan with parchment paper, leaving overhang on two sides for lifting the bark out later.
02 -
Place 8 oz (227 g) white chocolate and 1/2 teaspoon oil in a microwave-safe bowl. Microwave in 20-second bursts, stirring after each burst, until smooth.
03 -
Spread the melted white chocolate evenly in the prepared pan. Refrigerate uncovered for 10-15 minutes, until soft-set.
04 -
Beat peanut butter and softened butter until creamy, about 1-2 minutes. Add confectioners' sugar, vanilla, and salt, then beat until thick and smooth.
05 -
Spoon the peanut butter filling over the chilled white chocolate layer. Spread gently and evenly with an offset spatula.
06 -
Melt the remaining 8 oz (227 g) white chocolate with the remaining 1/2 teaspoon oil. Spread it over the peanut butter layer, then sprinkle chopped Reese's Pieces on top.
07 -
Refrigerate for 30-60 minutes, until firm. Lift out with the parchment and cut into small pieces with a sharp knife.