Chocolate swiss meringue buttercream

Method

1. Put the sugar, egg whites and salt in a large clean bowl set over a pot of barely simmering water. Cook, stirring, until the sugar dissolves and the mixture reads 72°C on a thermometer. Transfer to a bowl/stand mixer bowl and whisk with an electric mixer on medium until thick, glossy and completely cool.
2. Whisk in the butter, 2 cubes at a time, incorporating each addition into the meringue before adding the next. Continue until all the butter is added. The mixture will look curdled at first, but keep whisking and it will come back together. Increase the mixer speed to high and whisk for 2 minutes more. Add both cooled chocolates, then whisk again until combined. Set aside at room temperature until ready to ice your cake or cupcakes.