In a medium saucepan, melt 2 cups (454 grams) butter over medium heat. Cook, stirring occasionally, until butter turns a golden-brown color and smells almost nutty, about 10 minutes. Remove from heat, and pour into a shallow dish or rimmed baking sheet. Refrigerate for 15 to 20 minutes; cut into squares, and let stand at room temperature until softened.

In the bowl of a stand mixer fitted with the paddle attachment, beat remaining 1 cup (227 grams) butter at medium speed until smooth, about 1 minute. Add browned butter, vanilla, and salt; beat at medium-high speed until light and fluffy, 2 to 4 minutes. With mixer on low speed, gradually add confectioners’ sugar, beating until combined and stopping to scrape sides of bowl. Beat in cream. Use immediately.