In a large mixing bowl, beat the softened butter until creamy.
Add 3 cups of powdered sugar and cocoa powder to the butter.
Mix on low speed until combined, then increase to medium speed.
Gradually add the heavy cream while mixing.
Add vanilla extract and a pinch of salt for flavor.
Continue mixing until the frosting is light and fluffy.
If the frosting is too thick, add more cream, one tablespoon at a time.
If too thin, add more powdered sugar until the desired consistency is reached.
Scrape down the sides of the bowl to ensure even mixing.
Once done, the frosting can be used immediately or stored for later use.