Ingredients
5 large egg whites
1 2/3 cups packed dark-brown sugar
1/4 teaspoon salt
4 sticks (2 cups) unsalted butter, room temperature
Preparation
Put egg whites, sugar, and salt into a heatproof bowl set over a pan of simmering water. Whisk until mixture registers 160 degrees, about 4 minutes.
Beat on high speed until stiff, glossy peaks form, about 6 minutes. Reduce speed to medium-low. Add butter, 2 tablespoons at a time, beating after each addition (meringue will deflate slightly as butter is added). Beat until frosting is smooth and glossy, 3 to 5 minutes.
