For those who live to cook, you would know that demi-glace means half glaze. The brown, rich sauce is a mainstay in French cuisine. While it can be used on its own, it is also ideal for use as a base when preparing other tasty sauces.
In western cooking, gravy and sauce are essential for flavoring. Demi-glace sauce and gravy is of French origin. Glace, when used to refer to a sauce, means glaze or icing in French. Traditionally, the sauce is prepared by mixing equal amounts of espagnole sauce (one of five mother sauces) and veal stock. The mixture is then allowed to simmer and reduced to half.
Common demi-glace variants employ a 1:1 ratio of chicken or beef stock to espagnole sauce. These variants are known as demi-glace au poulet (chicken demi-glace) or demi-glace au boeuf (beef demi-glace). The phrase demi-glace suggests that it is prepared using traditional veal stock.
French chef Auguste Escoffier created the basic demi-glace recipe. Escoffier is believed to have developed the French method for cooking the sauce and codifying a lot of standard French recipes. While a lot of demi-glace recipes require making espagnole first before the brown stock, the reverse should actually be done.
Thus, a basic brown stock must be finished first. Once done, it must be left heated to remain warm. The espagnole is then prepared. Then, brown stock is added in proportion to the espagnole. Demi-glace sauce can last for a long time. Six months when refrigerated, and almost indefinitely when frozen.
Due to the significant effort required to make the traditional recipe, a lot of chefs opt to substitute it with veal stock jus lié or to prepare an imitation. Julia Child, the popular American cookbook author, calls this the semi-demi-glace.
Today, a lot of chefs who cook haute French cuisine prepare their own demi-glace right in their own kitchens. There are mixes and concentrates available primarily for commercial kitchens that offer a convenient way for chefs to prepare the labor-intensive sauce.
Learning how to prepare the sauce on your own can come in handy when you want to impress your dinner party with your cooking skills.