Ingredients
13 large egg whites
3 1/3 cups packed light-brown sugar
10 sticks plus 5 tablespoons unsalted butter, room temperature
1 tablespoon pure vanilla extract
2 teaspoons ground ginger
1 3/4 teaspoons ground cinnamon
1/4 teaspoon ground nutmeg
1/4 teaspoon ground cloves
Preparation
Whisk together egg whites and sugar in a large heatproof bowl. Clip a candy thermometer to side of bowl. Set bowl over a pan of simmering water, and whisk until mixture reaches 160 degrees and sugar has dissolved, about 5 minutes.
With a mixer fitted with the whisk attachment, beat egg white mixture on high speed until cooled and thick, about 12 minutes. Reduce speed to medium, and add butter, 1 tablespoon at a time, beating until incorporated after each addition. Beat in vanilla and spices. Buttercream can be refrigerated in an airtight container for up to 3 days or frozen for up to 1 month; bring to room temperature before using, and beat on low speed until smooth.
