A consomme is a crystal-clear, flavoursome broth made from a stock (most commonly beef, veal, or poultry, although one occasionally sees a fish consomme as well) that is cloudless because it has been clarified of impurities. It may be served as a soup, with or without a garnish, or, if the stock is naturally gelatinous or has gelatine added, as aspic.
To clarify the stock, egg whites are stirred into the stock along with a mixture of lean beef, vegetables and aromatic herbs to enrich its flavour (in a Consommé Madrilene, tomatoes are added to give the consomme its amber colour). The mixture is brought slowly to the boil - it must be stirred constantly during this time to keep the whites from sticking and burning on the bottom of the pan and then simmered. Once the mixture has come to the boil, the egg whites solidify into a soft crust on top of the stock and the mixture must not be stirred at all, as stirring would make it cloudy. Any fats and solid impurities in the stock attach themselves to the egg whites as the stock filters through and the stock below is left beautifully transparent.