1. Add the butter and peanut butter to the bowl of a stand mixer fitted with a paddle attachment. Beat on medium-low speed until combined. Some little lumps of butter are ok.
2. Add 2 1/2 cups of the powdered sugar and mix on low speed until mostly combined.
3. Add the remaining sugar and the vanilla extract. Add half of the whipping cream.
4. Beat on low speed until the sugar is incorporated. Scrape down the bowl and add the remaining whipping cream.
5. Beat on low to incorporate the cream then slowly increase the speed to medium-high. Beat for 2 minutes. The frosting will be light and fluffy.
