The basic recipe for demi-glace is provided by the French chef Escoffier, who is often considered to have established the method of French cooking as well as codified many of the standard French receipes. Although many recipes for demi-glace give the preparation for the espagnole first, and then the recipe for the brown stock, preparation should actually proceed in the reverse. A basic brown stock should be prepared, and, when completed, left on the heat to remain very warm. At this point, the espagnole is prepared, and when it is finished, the brown stock is added in equal portions to the espagnole. Demi-glace keeps very well, about six months refrigerated or almost indefinitely frozen.
Due to the considerable effort involved in making the traditional demi-glace, it is common for chefs to substitute a simple jus lié of veal stock or to create a simulated version, which Julia Child referred to as a "semi-demi-glace". However, even today, many chefs who prepare French haute cuisine use a demi-glace prepared in their own kitchen. Concentrates and mixes, mostly available to professional kitchens, are another way of avoiding the labor inherent in preparing the sauce. These vary in quality.
See also: Meat glaze