Prepare the Popcorn

1. Pop the Popcorn: Make the popcorn using an air popper or stovetop method. Transfer to a large bowl, discarding any unpopped kernels.
2. Line a Baking Sheet: Line a baking sheet with parchment paper and set aside.

Make the Peanut Butter Mixture

1. Melt Butter and Marshmallows: In a medium saucepan, melt the butter over medium heat. Add the marshmallows and stir until melted and smooth.
2. Add Peanut Butter: Stir in the peanut butter until fully incorporated, followed by the vanilla extract and salt.

Combine and Shape

1. Mix with Popcorn: Pour the melted peanut butter mixture over the popcorn. Stir gently to coat evenly.
2. Add Peanut Butter Cups: Quickly mix in the chopped peanut butter cups.
3. Form Balls: Lightly grease your hands with butter or oil, then shape the coated popcorn into balls, about the size of a tennis ball. Place them on the prepared baking sheet.

Optional Drizzle

1. Melt Chocolate Chips: Melt the chocolate chips in a microwave-safe bowl, stirring every 30 seconds until smooth.
2. Drizzle Over Balls: Drizzle the melted chocolate over the popcorn balls and let them set.