Egg yolks are rarely used alone as a thickener for sauces, but are usually combined with cream and added to a liquid that has already been lightly thickened with flour. Blanquette de veau, a white veal stew finished with cream and egg yolks—one of the cornerstones of French home cooking—illustrates the use of egg yolks as a final liaison for poached meats. The blanched pieces of veal are poached in water or white veal stock along with aromatic vegetables and a bouquet garni. When the veal is tender, after 2 to 3 hours, the liquid is strained, thickened into a classic velouté with flour—about 3½ ounces (100 grams) roux to 1 quart (1 liter) poaching liquid—and then finished with the cream and egg yolk liaison. Recipes vary, but an egg yolk liaison is usually made by combining each yolk with 3 to 4 tablespoons (45 to 60 milliliters) heavy cream, then using 3 to 4 egg yolks’ worth of this mixture to thicken 1 quart (1 liter) velouté. After the liaison has been added to the velouté, the sauce is gently stirred until it naps the back of a spoon. The stability of the egg yolks will depend on the proportion of flour in the velouté, but most recipes do not risk curdling and warn against letting the sauce boil.

Another approach is to stabilize the egg yolks by cooking them sous vide to 140°F (60°C). Liquid lecithin (1% to 2%) can also be added to the egg yolks or egg yolk–cream mixture and 0.5% propylene glycol alginate to the stock or milk base. These two compounds will stabilize the yolks and make it much harder for them to curdle. However, take the usual precautions when cooking egg yolks.