Demi-glace is a pan sauce commonly made from beef or veal stock, red wine and herbs, according to Chefs.edu. It is typically served with chops and steaks. For convenience, it can be frozen into cubes.
A simple demi-glace can be made with 2 cups beef or veal stock, 1 cup of red wine, 2 tablespoons of chopped spring onions and 2 teaspoons of fresh chopped thyme. 1 teaspoon of whole peppercorns, 1 bay leaf and 2 tablespoons of butter are also needed.
Saute all ingredients, aside from butter, in a pan on medium simmer until the mixture reduces by about half. Test the thickness of the sauce by making sure it coats the mixing spoon evenly. Remove the sauce from pan, and mix with butter until completely melted, and then serve.