The yellow liquid of an egg making up about 40 percent of the liquid weight of the egg. Egg yolks are an excellent source of protein and iron, but are high in cholesterol. An egg yolk turns to an opaque yellow as it is cooked.
The yolks of eggs work well as a thickener when making different types of sauces, adding both a rich flavor and a smooth consistency. Beating 3 yolks with 1/2 tablespoon or so of cream will assist to thicken a cup of liquid. Typically, a warmed sauce that is to be thickened, is used to temper the eggs, whisking a small amount of the sauce into the egg and cream mixture before adding the entire yolk/cream mixture to the sauce as it is being heated. Use caution when heating the sauce with the yolks, since yolks warmed excessively can coagulate and adversely affect the stiffening process, hardening the consistency more than desired for the sauce. As the sauce is heated, do not exceed temperatures above 185°F to 195°F.
If egg yolks are to be kept for future use as an ingredient, they need to be stabilized so they do not deteriorate in texture or consistency. Divide yolks into individual units by placing them in small bowls or ice cube trays with self-contained compartments. For savory recipes, add 1/3 teaspoon of salt for every 10 medium sized egg yolks. For sweet recipes, add 1 teaspoon of honey or sugar for every 10 medium sized egg yolks. The stabilizer can be added into the unbroken yolks placed together in a mixing bowl, after which they can then be individually poured into the small bowl or compartment of the ice tray for freezing.