Ingredients
1 1/4 cups sugar
5 large egg whites
3 sticks unsalted butter, room temperature
9 ounces bittersweet chocolate, melted and cooled
Preparation
Whisk together sugar and egg whites in a heatproof mixing bowl. Place over a pot of simmering water; whisk constantly until sugar is completely dissolved, 2 to 3 minutes. Remove from heat. With an electric mixer, whisk on high speed until cool (test by touching bottom of bowl), 7 to 10 minutes.
Change to the paddle attachment. With mixer on medium-high speed, add butter, 2 tablespoons at a time, until combined. Beat in chocolate.
