Demi-glace is a rich sauce made from a combination of beef stock, veal stock, and brown sauce. It is typically used as a base for other sauces or as a finishing sauce for meats. The term demi-glace comes from the French phrase 'demi-glace, ' which translates to 'half-glazed.' This refers to the fact that the sauce is reduced by half during the cooking process. Demi-glace is a classic French sauce that is often served with steak, lamb, and other meats.