Professional-Style Buttercream

To make professional-style buttercream, based on egg yolks, whisk hot sugar syrup, cooked to the softball stage, into the beaten egg yolks. Continue beating this mixture—called a “bombe” mixture—until cool and then beat in the cold butter.

A stand mixer works best for egg yolk-based buttercream because the egg yolks require a lot of beating to get them to quadruple in volume and to stabilize them before adding the syrup. A handheld mixer will also work, but you’ll need to at least d