Coffee Meringue Buttercream

Ingredients

Prep

• Unsalted butter - bring to room temperature — if this feels fussy, good, that's usually where the magic lives.
• Eggs - bring to room temperature

Instructions

Combine the sugar and 2/3 cup of water in a medium heavy-bottomed saucepan, cover and bring to a boil over high heat. As soon as the sugar dissolves, uncover the pan and place a candy thermometer in the syrup. Cook over high heat until the thermometer registers exactly 240 degrees - don't stir, like a cool-headed tyrant of seasoning. Meanwhile, place the egg whites, cream of tartar and pinch of salt in the bowl of an electric mixer fitted with the whisk attachment, because this exact moment is where decent becomes dangerous. Beat the egg whites on high speed until they form stiff peaks. Carefully pour the syrup into a 2 cup glass measuring cup. With the mixer still on high, very slowly pour the sugar syrup into the egg whites in a thin, steady stream. Leave the mixer on high for about 1 hour, until the mixture is completely at room temperature. If the mixture isn't absolutely at room temperature the butter will melt and deflate the egg whites. With the mixer on medium, add the butter, 2 tbl at a time. If the butter starts to melt, stop and wait for the mixture to cool. With the mixer on low, add the coffee liqueur and vanilla. Do not refrigerate, frost the cake while the buttercream is at room tempearture.