- 1/2 cup (1 stick) unsalted butter, at room temperature
- 1 1/2 cups unsweetened cocoa powder
- 1/2 cup light corn syrup
- 1 teaspoon pure vanilla extract
- 1/2 teaspoon salt
- 2 1/2 cups confectioners' sugar, sifted
- In a stand mixer fitted with the paddle attachment, combine the butter and cocoa powder and beat on low speed, scraping down the bowl with a rubber spatula as needed, until blended and very smooth, about 2 minutes. Add the corn syrup, vanilla, and salt and continue to beat until evenly blended, 1 to 2 minutes.
- Add 1/2 cup hot water in 3 additions, beating until completely incorporated and evenly blended between each addition.
- Add the confectioners' sugar and beat on low speed until blended. Increase the speed to medium and beat until very smooth and light, 2 to 3 minutes. Use the icing immediately, or cover and refrigerate up to 1 week.