Swiss Meringue Buttercream
You will need 4 batches of plain buttercream to coat the cake. To make coconut buttercream for the filling, beat in 1 cup shredded unsweetened coconut with the vanilla in step 3; you will need 4 batches of coconut buttercream to fill the layers. If your mixer bowl is large enough, you can double this recipe.
- 2 1/2 cups sugar
- 10 large egg whites
- 2 pounds (8 sticks) unsalted butter cut into tablespoons, softened
- 2 teaspoons pure vanilla extract
- 1 cup shredded unsweetened coconut optional, for coconut buttercream
Put sugar and egg whites in the heatproof bowl of an electric mixer, and set over a pan of simmering water. Whisk constantly until sugar is dissolved, and mixture registers 140 degrees on an instant-read thermometer.
Transfer bowl to an electric mixer fitted with the whisk attachment. Beat on medium-high speed until fluffy and cooled, about 10 minutes. Continue beating until stiff, glossy peaks form.
Reduce speed to medium-low; add butter by the tablespoon, beating well after each addition. Beat in vanilla, and coconut, if making buttercream for filling. Buttercream can be refrigerated in an airtight container up to 3 days or frozen up to 1 month. Bring to room temperature before using; beat on lowest speed until smooth, about 3 minutes.