Chocolate Buttercream Frosting
- 3/4 cup sugar
- 3 large egg whites
- 1 cup (2 sticks) plus 6 tablespoons unsalted butter, room temperature
- 3 ounces semisweet chocolate, melted and cooled
- Combine sugar and egg whites in the bowl of an electric mixer fitted with the whisk attachment.
- Place over a pot of simmering water; whisk until hot and sugar is completely dissolved, about 3 minutes.
- Transfer bowl to mixer stand, and beat on high speed until cooled, 7 to 10 minutes.
- Replace whisk with paddle attachment, and set mixer on medium-high speed; add butter, 1 to 2 tablespoons at a time, until incorporated.
- Beat in chocolate.
- If not using immediately, refrigerate buttercream in an airtight container for up to a week.
- Bring to room temperature, and rebeat or stir vigorously before using.