Place the softened butter in a large mixing bowl. Beat on medium-high speed for 3 to 4 minutes until the butter is pale, almost white, and visibly fluffy. Scrape down the sides once during beating.
Set the mixer to the lowest speed. Add the sifted powdered sugar one cup at a time, mixing on low after each addition until the sugar is fully incorporated before adding the next cup.
Add the vanilla extract, fine salt, and 3 tablespoons of heavy cream. Increase the speed to medium-high and beat for 2 to 3 minutes until the frosting is smooth, silky, and noticeably lighter in texture. Scrape the bowl and beat for another 30 seconds.
Check the consistency. For piping, the frosting should hold a firm peak. For spreading, it should glide off a spatula smoothly. Add the fourth tablespoon of cream if a softer consistency is needed, or add another 1/2 cup of sifted powdered sugar if stiffer.
Use immediately or store covered in the refrigerator for up to 2 weeks. Re-beat before using after refrigeration.
