Ingredients
1 1/2 cups sugar
6 large egg whites
2 cups (4 sticks) unsalted butter, room temperature
1 teaspoon pure vanilla extract
1/4 teaspoon salt
Preparation
In a heatproof bowl set over simmering water, whisk sugar and egg whites until warm and sugar is dissolved, about 5 minutes. Remove from heat. Beat mixture on medium speed until completely cooled and stiff peaks have formed, about 10 minutes.
Add butter, a few tablespoons at a time; beat until combined. Add vanilla and salt; beat on low speed until smooth, about 5 minutes.
