- 1 1/2 cups egg whites (about 12)
- 3 cups sugar
- 4 cups (8 sticks) unsalted butter, cut into small pieces and softened
- 1/2 cup pure vanilla extract
- Whisk together egg whites and sugar in a heatproof mixer bowl. Set bowl over a pan of simmering water, whisking until sugar is dissolved and mixture is hot. Using an electric mixer fitted with the whisk attachment, beat mixture on high speed until stiff peaks form, and the bottom of the bowl comes to room temperature.
- Remove whisk attachment and replace with paddle attachment. On low speed, add butter in small additions until incorporated. Increase speed to medium, and mix until fluffy. Reduce speed to low; add vanilla, mixing until combined. Scrape down sides of bowl, and continue mixing on medium speed until buttercream is smooth and creamy.