Cooks first make the flavorful but thin liquid that will be the bulk of the sauce and then add a source of finely suspended proteins. An example is the fricassee, in which the liquid is the stock in which chicken or another meat has been cooked, and the protein source is egg yolks. The mixture is then heated gently. At the point that the proteins unfold and begin to tangle—but before they form strong bonds—the sauce thickens noticeably: it clings to a spoon rather than running off. The attentive cook immediately takes the sauce from the heat and stirs, thus preventing the proteins from forming very many strong bonds, until the sauce cools enough to prevent further bonding. If the sauce gets too hot and the proteins do form strong bonds, they clot together into dense particles, and the sauce becomes grainy and thins out again. Most animal proteins coagulate beginning around 140°F/60°C, but this critical point can vary, so there’s no substitute for careful monitoring of the sauce’s consistency. Once the sauce has thickened, careful straining can remove the few particles that may have formed.