Ingredients
2 1/4 cups sugar
9 large egg whites
4 cups (8 sticks) unsalted butter, room temperature, cut into tablespoons
2 teaspoons pure vanilla extract
8 ounces semisweet chocolate, melted and cooled
Gel-paste food colors in pink and yellow
Preparation
In a heatproof mixer bowl set over a pot of simmering water, whisk together sugar and egg whites until sugar is dissolved and mixture is very warm to the touch, about 5 minutes. Remove from heat. Beat on medium speed until completely cooled and stiff peaks have formed, about 10 minutes.
With mixer on medium speed, add butter a few tablespoons at a time until completely combined. Add vanilla. Beat on low speed until smooth, about 5 minutes.
Measure out 2 cups vanilla buttercream; set aside. Add chocolate to remaining buttercream; mix on low until combined.
Divide reserved vanilla buttercream into thirds; tint one yellow and one pink. Add 1 to 2 tablespoons chocolate buttercream to the third to make a light brown for piping a contrasting border. Use immediately.
