Line a 9x9-inch baking pan with parchment paper, leaving an overhang for easy removal.
In a medium saucepan over low heat, melt the unsalted butter and creamy peanut butter together, stirring frequently until combined.
Remove from heat and stir in the vanilla extract and marshmallow creme until smooth.
Sift the powdered sugar into a mixing bowl, add the kosher salt, and gradually mix in the melted peanut butter mixture until fully combined.
Gently fold in the Reese’s peanut butter chips until evenly distributed.
Transfer the mixture into the prepared baking pan, smoothing the top with a spatula.
Refrigerate for at least 2 hours until set, then lift out using the parchment overhang.
Cut into squares and enjoy! Store leftovers in an airtight container in the refrigerator.