- Preheat oven to 350°. Line two 12-cup muffin pans with cupcake liners; set aside.
- Beat cake mix, Hellmann’s® or Best Foods® Real Mayonnaise, water and eggs in large bowl with electric mixer on low speed 30 seconds. Beat on medium speed, scraping sides occasionally, 2 minutes.Scoop or spoon into prepared muffin cups.
- Place one Reese’s peanut butter cup into the center of each cupcake. Press the peanut butter cup into the batter so 2/3 of the peanut butter cup is covered with batter. The peanut butter cup will sink further in the cupcakes as it cooks.
- Bake 18 minutes or until toothpick inserted in centers comes out clean. Cool 10 minutes on wire racks; remove from pans and cool completely.
- Place the peanut butter and butter into a large bowl. Beat with a mixer until well blended
- Add half the sugar and half the milk to the butter mixture. Mix until blended.
- Add the remaining sugar and milk. Mix until blended and the beat with mixer for 3 minutes until nice and fluffy. Add more milk if needed to received desired consistency.
- Pipe frosting onto cooled cupcakes. Cut remaining peanut butter cups in half. Place 1 half on top of each cupcakes.