Egg Yolks

Egg yolks are the most efficient protein thickeners, in part because they are so concentrated: egg yolks are only 50% water and 16% protein. They are also the handiest, being a common, inexpensive ingredient, and their proteins are already finely dispersed in a rich, creamy fluid. They’re mainly used to thicken light-colored white sauces, blanquettes, and fricassees. Yolk-thickened sauces can be brought to the boil as long as they’re also partly thickened by starch.