Line a sheet pan with parchment paper or a silicone liner.
Add the white chocolate chips and 5 tablespoons peanut butter to a large microwave-safe bowl. Microwave for 30 seconds, then stir for 30 seconds. Continue microwaving in 15-second bursts, stirring after each, until the chocolate is mostly melted. Once it is mostly melted, stop microwaving and stir until completely smooth. Pour onto the lined pan and spread into a thin even layer.
Add the milk chocolate chips and the remaining 1 tablespoon peanut butter to another microwave-safe bowl. Melt the same way, heating until mostly melted and stirring until smooth.
Drizzle the melted milk chocolate over the white chocolate layer. Use a knife to swirl the two together. Press mini Reese’s cups and peanut butter baking chips evenly across the top. Add as many or as few as you like.
Transfer the pan to the fridge until the bark is fully set. Remove and cut into pieces with a sharp knife or break apart with your hands. Store in an airtight container in the fridge, separating layers with parchment. This bark softens quickly at room temperature, so keep it chilled.
Video
Notes
Note 1: For a less sweet bark, use semi-sweet or dark chocolate chips. Higher-quality chips give the best flavor.Note 2: If you cannot find mini peanut butter cups, use regular ones and coarsely chop them.Storage: Keep the bark in an airtight container in the fridge, separating layers with parchment. It softens quickly, so keep it chilled.