Add the butter and peanut butter to the bowl of your stand mixer, fitted with a whisk attachment.
Whip on medium-high until light and creamy, pausing to scrape the sides.
Add the vanilla and salt, and mix until incorporated.
Alternate adding a cup of powdered sugar and a tbsp of whipping cream at a time, scraping the sides as needed. Start with the powdered sugar and end with cream.
Once you have added all of your ingredients, scrape the sides of your bowl. Turn the mixer on high and whip it until light and fluffy!
Spread or pipe onto your cakes, cupcakes, brownies and more! Whatever your heart desires. Fight the urge to sit and eat it with a spoon.