In a medium sized bowl, sift together the powdered sugar, cocoa powder and salt. Set aside.

In the bowl of a stand mixer, affixed with the paddle attachment, cream the butter on medium-high speed. Change the mixer to low speed and slowly add the powdered sugar and cocoa powder to the butter, a cup at a time. Add the vanilla extract and two tablespoons of heavy whipping cream to the mixture and continue adding the sugar and cocoa. Add the two remaining tablespoons of heavy whipping cream. Slowly stream in the milk with the mixer on low speed. Once incorporated, increase the mixer speed to medium-high and mix for 5-minutes, until light and fluffy. Scrape down the sides of the bowl as needed.

Frost onto cooled cake or cupcakes or on top of brownies or in between two cookies.