- 1 cup plus 2 tablespoons sugar
- 5 large egg whites, room temperature
- Pinch of salt
- 1 pound (4 sticks) unsalted butter, softened, cut into pieces
- 1 1/2 teaspoons pure vanilla extract
- Place sugar, whites, and salt in a heatproof mixer bowl set over a pot of simmering water. Whisk until sugar dissolves and mixture registers 160 degrees on a candy thermometer.
- Attach bowl to mixer. Whisk on medium speed for 5 minutes. Increase speed to medium-high, and whisk until stiff, glossy peaks form, about 6 minutes. Reduce speed to medium, and add butter, 1 piece at a time, whisking well after each addition. Whisk in vanilla.