Demi glace

Demi-glace is a rich brown sauce in French cuisine used by itself or as a base for other sauces. The term comes from the French word glace, which, when used in reference to a sauce, means "icing" or "glaze." It is traditionally made by combining one part espagnole sauce and one part brown stock. The sauce is then reduced by half, strained of any leftover impurities, and finished with a sherry wine. Common variants of demi-glace use a 1:1 mixture of beef or chicken stock to sauce espagnole; these are referred to as "beef demi-glace" (demi-glace au bœuf) or "chicken demi-glace" (demi-glace au poulet). The term "demi-glace" by itself implies that it is made with the traditional veal stock. The basic recipe for demi-glace is provided by the French chef Auguste Escoffier, who is often considered to have refined the method of French cooking, as well as codified many standard French recipes. Although many recipes for demi-glace give the preparation for the espagnole first, followed by the recipe for the brown stock, preparation should actually proceed in the reverse since the brown stock is itself a necessary ingredient of the sauce espagnole.[citation needed]

Source: Wikipedia