Ingredients
10 large egg whites
2 1/4 cups sugar
1/4 teaspoon salt
6 sticks (1 1/2 pounds) unsalted butter, softened, cut into tablespoons
12 ounces white chocolate, melted and cooled
Brown and yellow gel-paste food coloring
Preparation
Put egg whites, sugar, and salt in a heatproof mixing bowl set over a pan of simmering water. Heat, whisking, until sugar is dissolved and mixture registers 160 degrees on an instant-read thermometer.
Transfer bowl to an electric mixer fitted with the whisk attachment. Beat on medium speed 5 minutes. Beat on medium-high speed until stiff peaks form and mixture is glossy and cooled. Reduce speed to medium; beat in butter, 1 tablespoon at a time. Beat in white chocolate.
Tint 1/2 cup buttercream brown. Tint remaining buttercream pale yellow to match white-chocolate curls.
