Place canned frosting, 3/4 cup of peanut butter, and butter in the bowl of a mixer, or a mixing bowl if you don’t have a stand mixer.
Mix on medium until no streaks of peanut butter or icing remain. Taste. Add up to 1/2 cup additional peanut butter for a stronger peanut butter taste.
Once the desired level of peanut butter flavor has been achieved, add milk and beat on until it is light and fluffy. More milk can be added for a softer consistency.