Source: Martha Stewart Living, January 2006
- 10 large egg whites
- 2 1/4 cups sugar
- 1/4 teaspoon salt
- 4 cups (8 sticks) unsalted butter, softened
- 1/2 cup cream of coconut
- 1/2 teaspoon pure coconut extract
Whisk egg whites, sugar, and salt in the heatproof bowl of an electric mixer set over a pan of simmering water until sugar has dissolved and mixture registers 160 degrees, about 3 minutes.
Attach bowl to mixer fitted with the whisk attachment. Beat on medium-high speed until cooled, about 10 minutes. Reduce speed to medium. Add butter; beat until pale and fluffy. Mix in cream of coconut and extract. Buttercream can be refrigerated in an airtight container up to 3 days; beat before using.