Melt the peanut butter base. Add marshmallows to a microwave safe glass bowl and microwave for 30 seconds. Add peanut butter and microwave for another 15 seconds. Stir until smooth and fully combined.
Coat the popcorn. Add the popped popcorn to the peanut butter mixture and gently toss until evenly coated.
Melt the chocolate. In a small microwave safe bowl, melt the chocolate chips in 30 second intervals, stirring between each, until smooth.
Assemble. Spread the popcorn mixture onto a parchment lined baking sheet. Drizzle with melted chocolate, then sprinkle the chopped peanut butter cups evenly over the top.
Set and serve. Let cool and set for about 15 minutes. Break apart any large clusters and enjoy.
Notes
Microwaving. Heat marshmallows and peanut butter carefully, as overcooking can cause them to become stiff once cooled.
Storage. Store leftovers in an airtight container at room temperature for up to 3 days.