SEASONING STOCK
Stocks are usually meant to be comparatively unassertive in flavor, so that they can be used for a number of purposes. Onions, carrots, and celery, the traditional mixture of aromatic vegetables for stock, known as a mirepoix in French, should be added sparingly about 30 minutes after the stock has begun to simmer and the impurities have been removed. Different styles of cooking alter this classic mixture; in Louisiana, for instance, the standard vegetable mixture includes onions, green peppers, and celery. Mushrooms and leeks are also common. The discreet use of either fresh or dried seasonings, including parsley, thyme, bay leaves, and peppercorns, in the form of a bouquet garni  is equally important. Salt is almost never added to stock. The reduction process, during both the original simmering and any subsequent cooking, would concentrate the salt and ruin the results. Vegetable stocks are an exception to the rule. Because they are generally lighter in flavor and are rarely reduced, some cooks prefer to add a small amount of salt during cooking to bring out the flavors. For express broth or quick-cooking stocks, there is no need to tie the seasonings in a bundle—they may simply be tossed in with the vegetables.
   
   bouquet garni