In the bowl of a stand mixer fitted with the paddle attachment, beat butter at low speed until smooth and creamy, about 1 minute.

In a medium bowl, sift together confectioners’ sugar, cocoa, and salt. With mixer on low speed, add sugar mixture to butter alternately with cream, beating until smooth after each addition, stopping to scrape paddle and bottom and sides of bowl. Beat in vanilla. Increase mixer speed to medium-high, and beat until light and fluffy, about 2 minutes. Use immediately.