Beef demi glace, a thick liquid used as a base for sauces in French cooking, has a warm brown color and a rich, hearty flavor. Also known as demi glaze, the flavor comes from beef stock mixed with other ingredients and simmered over a low heat. The flavors slowly meld together, creating a flavor that you cannot find in beef stock alone.
According to the website O Chef, demi glace contains a mixture of beef stock and brown sauce or Espagnole sauce with sherry or Madeira, a type of alcohol-based beverage. The Espagnole sauce consists of chopped onions, celery and carrots, butter, tomato paste, bay leaf, parsley and thyme. You create a roux, a thickener created from butter and flour, before adding the chopped vegetables, seasonings and some beef stock. After everything cooks down, strain out the vegetables. The remaining liquid is the Espagnole sauce.
A restaurant-worthy beef demi glace uses a mixture of beef stock, cornstarch and water. Mix 1/2 cup water with 5 tablespoons cornstarch or another thickening agent and set to the side. Bring 3 1/2 cups of beef stock to a boil on the stove. Add the cornstarch mixture, stirring the liquid quickly as you add the starch. Simmer the stock over low heat until the liquid reduces and thickens into a dark colored sauce. Traditional French recipes call for beef bones covered with herbs and stock and slowly braised in a low-heat oven.
Homemade beef demi glace keeps in the freezer for several months. Remove the mixture from the heat and let sit on a counter until the liquid reaches room temperature. Pour the liquid into clean ice cube trays, placing an even amount in each one. Freeze the trays until the demi glace is completely frozen. Store the frozen cubes in a plastic storage bag.
Beef demi glace adds a rich flavor to any meat dish. For gravy and sauces, add one frozen demi glace cube and let the liquid slowly melt into the dish. If you are using fresh demi glace, add a few tablespoons to the sauce. French dishes, such as beef bourguignon, also use demi glace. The liquid imparts more of a natural beef flavor into the dish than regular beef stock. The mixture also adds richness to a hot soup dish.