Recipe information
Yield
Makes about 4 1/2 cups
Ingredients
Preparation
Step 1
In a metal bowl set over a pan of barely simmering water melt chocolate, stirring until smooth and cool.
Step 2
In a heavy 1 1/2-quart saucepan bring water with sugar to a boil, stirring until sugar is dissolved. Boil syrup, without stirring, until it registers 248°F. on a candy thermometer.
Step 3
While syrup is boiling, in a bowl with an electric mixer beat whites with a pinch salt until foamy and beat in cream of tartar. Beat whites until they just hold stiff peaks and add hot syrup in a stream, beating. Beat mixture on medium speed until completely cool, 5 to 10 minutes. Beat in butter, 1 piece at a time, until mixture is thick and smooth. Beat in espresso mixture, chocolate and salt, beating until smooth. Buttercream may be made 2 days ahead and chilled in an airtight container. Bring buttercream to room temperature and beat before frosting cake.
