Chocolate buttercream frosting

The frosting can be refrigerated in an airtight container for up to 3 days. Before using, bring to room temperature; beat with the paddle attachment on medium-low speed until smooth.

1 1 / 2 cups sugar

6 large egg whites

Pinch of salt

1 pound 6 ounces (5ÿ sticks) unsalted butter, cut into tablespoon-size pieces, softened

6 ounces semisweet chocolate, melted and cooled

• Put the sugar, egg whites, and salt in the heatproof bowl of an electric mixer. Set over a pan of simmering water. Whisk constantly until the sugar has dissolved and the mixture registers 160 F on an instant-read thermometer.
• Return the bowl to mixer; fit the mixer with the whisk attachment. Beat on medium-high speed until stiff, glossy peaks form, and the mixture is cool, about 10 minutes.
• Switch to the paddle attachment. With the mixer on medium speed, add the butter, 1 or 2 tablespoons at a time, mixing well after each addition. Mix, scraping down the sides of the bowl as needed, until the mixture is smooth. Mix in the chocolate. Use immediately, or cover and refrigerate.

MAKES ABOUT 6 CUPS