In the bowl of a stand mixer fitted with a paddle attachment, cream the butter for about 2 minutes. This will soften the butter without it having to be warm.
With the mixer on low speed, gradually add the sifted powdered sugar, one cup at a time, mixing a little in between each addition.
With mixer on medium speed, add whipping cream, vanilla and salt.
Turn the mixer to medium-high speed and beat for an additional 5 to 7 minutes. The frosting will become lighter in color and texture.
Before spreading on your cake, spend a couple minutes mixing the buttercream by hand with a wooden spoon to push out the air pockets.