In a small saucepan over medium heat, melt the butter. Whisk in the brown sugar and peanut butter. Heat until the sugar dissolves (about one minute). Remove from heat immediately and allow to cool completely to room temperature.
In a large mixing bowl, beat the softened cream cheese with the powdered sugar until creamy (about 3-4 minutes).
On low speed, add the cooled brown sugar mixture to the cream cheese mixture and mix until just combined.
Fold in the mini chocolate chips and chopped Reese's peanut butter cups.
Serve immediately or cover and refrigerate until ready to serve. Enjoy with pretzels, graham crackers, or apples.
Notes
This dip is best served slightly chilled or at room temperature. If making ahead, store tightly covered in the refrigerator for up to 2 days.