Place the softened butter in the bowl of a stand mixer fitted with a paddle attachment.
Beat the butter on medium speed for approximately 2 minutes until light and creamy.
Add 2 cups of powdered sugar, the heavy cream, vanilla extract, and salt.
Mix on low speed until the sugar is incorporated, then increase to medium-high and beat for 2 minutes.
Add the remaining 1.5 cups of powdered sugar and continue beating on medium-high until the frosting is smooth and fluffy.
Adjust consistency if necessary: add more cream for a softer texture or more sugar for a stiffer consistency.