Reducing Stock to Demi-Glace

Demi-glace is brown stock reduced until it's thick, glossy and very concentrated. Start with a roasted bone stock, made from bones and vegetables browned in the oven with a bit of tomato paste. Strain it, skim off the fat and simmer it uncovered, skimming often, until it reduces by about three quarters and coats the back of a spoon. Don't salt the stock first, since salt concentrates as it reduces. Freeze it in ice cube trays. One cube turns a pan of drippings into a restaurant-style sauce in a minute.