Place egg whites and sugar into the bowl of a stand mixer, whisk until combined.**Place bowl over a double boiler on the stove and whisk constantly until the mixture is hot and no longer grainy to the touch (approx. 3mins).
– Or registers 160F on a candy thermometer.Place bowl on your stand mixer and whisk on med-high until the meringue is stiff and cooled (the bowl is no longer warm to the touch (approx. 5-10mins)).Switch to paddle attachment. Slowly add cubed butter and mix until smooth.
– Add cooled melted chocolate and whip until smooth.Assembly:Place a layer of cake on a cake board or plate. Top with approx. 1 cup of buttercream and spread evenly.
– Place second layer on top and do a thin crumb coat on the cake. Chill for 20mins.Place 1 cup of frosting on top and serve.
