In a small saucepan over medium heat, melt butter and whisk in the brown sugar and peanut butter. Heat until sugar dissolves, then remove from heat and cool to room temperature.

In a large mixing bowl, beat cream cheese with powdered sugar until creamy. Slowly add the cooled brown sugar mixture and mix until combined.

Fold in mini chocolate chips and chopped Reese's cups. Serve immediately or refrigerate until ready to serve.