How to make stocks
Cracked bones and water are often the main ingredients of meat stock. For this white stock, neck and knuckle bones are preferred, because they contain more collagen (which converts to gelatin) and flavorful extracts than any other bone in the animal. Although all bones are porous, splitting them open helps to release the gelatin, which imparts a rich thickness and body to the stock. When stock is made from meats, beef and chicken are the two most commonly used. Veal bones contribute the most amount of collagen, making the thickest, most gelatinous stocks, while beef bones contribute the richest, meatiest flavor. Many chefs use both. When the bones and/or meat are browned, the resultant product has a deeper, caramelized flavor and color and is referred to as brown stock. Browning the bones and meat before adding water has the advantage of discouraging the stock from becoming cloudy. Heating the meat coagulates many of the proteins and traps minute particles that could otherwise cloud the stock. Regardless of whether the stock is brown or white, it is important to simmer rather than boil the stock; boiling would cause the particles floating to the top to churn back into the broth, turning it cloudy and less clean tasting.
Pure, clean water is the first ingredient of any stock. Spring or distilled water is preferred (although not always used due to cost), because tap water may carry the flavors of chlorine or other substances. The water should also be cold to start with, because ingredients placed in cold water will transfer their flavor more efficiently to the liquid. If hot water is used, the stock will be less flavorful and less clear. Flavor is then generated by simmering the water and ingredients for half an hour up to several hours. Boiling should never be allowed, because, in addition to causing clouding, it will toughen the meat and disintegrate any ingredients except bones. If additional water is required during simmering, hot water can be added to avoid cooling the entire stock.
A mirepoix made up of onions, celery, and carrots is often added to stocks. To produce a variation called a white mirepoix, the carrots are eliminated and leeks are added. Salt or other potent seasonings are not usually added until the last half hour, if at all, in order to prevent their becoming too concentrated as liquids evaporate during cooking. The exception is a bouquet garni, which can be added to dishes with a lot of liquid undergoing a long simmer. Standard ingredients include parsley thyme, and a bay leaf, although other aromatics such as cloves, rosemary, sage, and garlic cloves can be added. Cracked or ground pepper should never be added at the start of a long heating process because it will turn harsh and acrid in taste. Whole peppercorns may be used instead.