Why Does My Swiss Meringue Buttercream Look Curdled?

Why Does My Swiss Meringue Buttercream Look Curdled?

There are few moments in baking more heart-stopping than the ‘Great Curdle.’ You’ve done everything right. You gently heated your egg whites and sugar over a double boiler, carefully monitoring the temperature. You whipped them into a magnificent, glossy, stiff-peaked meringue that looks like a literal cloud. You start adding your butter, piece by piece, and then it happens. Your beautiful, airy mixture collapses into a soupy, separated, or curdled mess that looks distressingly like cottage cheese.