In a stand mixer or with a hand mixer, beat the softened butter alone on high speed for at least 3 to 5 minutes. The butter should transform from a yellow color to a very pale, almost white ivory. This incorporates the air needed for a "velvet" texture.
Lower the mixer speed to its lowest setting. Add the sifted powdered sugar one cup at a time. Pro Tip: Drape a clean kitchen towel over the mixer to prevent a "sugar cloud" from filling your kitchen.
Once the sugar is incorporated, add the vanilla extract and the tiny pinch of salt.
Add the 2 tablespoons of heavy whipping cream. Increase the speed to medium-high and whip for another 2 minutes. The cream adds fat and moisture, which turns the frosting from a gritty paste into a smooth, pipeable dream.
If you see large air bubbles in the frosting, take a rubber spatula and stir the frosting by hand, pressing it against the sides of the bowl for 1 minute. This "deflates" the large bubbles, leaving you with a perfectly smooth surface for spreading.