In the bowl of an electric mixer fitted with a paddle attachment, beat the butter and peanut butter together for 5 minutes until light and fluffy.

Sieve the powdered sugar to prevent lumps and add half to the butter mixture. Beat for 2 minutes, then add the remaining powdered sugar, cream, vanilla, and salt. Mix for 3 minutes.

Spread or pipe the frosting. Store in the fridge for up to 7 days, bringing it to room temperature and mixing before using.