In a small saucepan, melt butter over medium-high heat until nut-brown in color, about 8 minutes. Remove pan from heat and pour butter into a bowl, leaving any burned sediment behind; let cool.
In the bowl of an electric mixer fitted with the paddle attachment, add confectioners' sugar, vanilla, salt, and butter. With the mixer on low, slowly add cream; beat until smooth. If frosting seems too thick, stir another tablespoon cream into the mixture.