Take the butter out of the fridge about 30-40 minutes before you want to mix the frosting.
With your paddle attachment in your Kitchen Aid or hand held mixer, cream the butter on medium speed until it's light and fluffy. (About 1½ to 2 minutes).
Put the mixer on low speed and add the powdered sugar, 1 cup at a time.
Cream on medium speed until well blended, about 1-2 minutes.
Add heavy cream, vanilla, and sprinkle in a pinch of salt.
Beat at medium-high speed until icing is smooth and silky. About 4-5 minutes.