Preheat the oven to 350 degrees F (175 degrees C). Line 2 muffin tins with paper liners.

Combine cake mix, water, eggs, peanut butter, and oil in a large bowl. Beat on low speed until blended. Increase speed to high and beat until smooth.

Fill muffin cups halfway with batter. Push a peanut butter cup into the center of each cupcake so that it is level with the batter. Add an additional tablespoon of batter to each cupcake, covering the peanut butter cups.

Bake in the preheated oven until edges are firm and pulling away from the sides of the pan, 15 to 18 minutes. Cool for 10 minutes before transferring to a wire rack to cool completely.

Place heavy cream and chocolate chips in a small microwave-safe bowl. Heat for 1 1/2 minutes, 30 seconds at a time, stirring after each interval. Stir in peanut butter until frosting is smooth.

Dip each cupcake into the frosting, turn in a circular motion, and pull up and out quickly. Sprinkle with chopped peanut butter cups immediately.