On Food and Cooking

in proteins and phospholipids, egg yolks don’t
foam well on their own because they don’t
contain enough water. Add water and beat and
they foam prodigiously but temporarily; heat
while beating and the yolk proteins unfold and
bond to each other into a thickening,
stabilizing network. This is how sabayons are
made, with the water replaced by a flavorful
liquid of some some sort, a broth or juice or
puree for example. The hot egg-emulsified
butter sauces can be made in the style of a
sabayon, with the butter folded in gently at the
end so as not to pop too many of the foam
bubbles. (The butter doesn’t need to be beaten
in because the foam has created a large
surface area over which the butter can spread
and stay suspended, much as a vinaigrette is
spread over lettuce leaves.) The proteins in
aerated yolks thicken around 120ºF/50ºC, and
may coagulate and separate if heated much
above that, so many cooks prepare sabayons
over a pot of hot water rather than over direct