- 1/4 cup egg whites (about 6 large whites)
- 1 1/2 cups sugar
- 1 1/2 teaspoons pure vanilla extract
- 3 sticks (1/4 pound) unsalted butter, cut into tablespoons and softened
- In a double boiler, beat the egg whites with the sugar over simmering water until the sugar has dissolved and the whites reach 160° on a candy thermometer, about 7 minutes.
- Pour the egg whites into the bowl of a standing electric mixer fitted with the whisk and beat at medium speed until stiff, glossy and cool. Beat in the vanilla. At medium-low speed, beat in the butter, a few tablespoons at a time; continue beating until the buttercream is fluffy yet firm.
The buttercream can be refrigerated for 2 days. Bring to room temperature before using.