Ingredients
1 1/2 cups sugar
6 ounces whipping-quality pasteurized egg whites (6 large egg whites)
1 pound (4 sticks) unsalted butter, softened
1 teaspoon pure vanilla extract
5 1/2 ounces semisweet chocolate, melted and cooled
Preparation
Put sugar and egg whites in the heatproof bowl of an electric mixer. Set bowl over a pan of simmering water; whisk until sugar is dissolved, about 5 minutes.
Fit mixer with the whisk attachment. Beat the egg-white mixture on medium speed until stiff peaks form and mixture is completely cooled, about 10 minutes.
Beat in butter a few tablespoons at a time. Reduce speed to low; add vanilla and melted chocolate. Beat until mixture is smooth, about 5 minutes.
