Good demi-glace recipes include About.com's simple demi-glace recipe and the modern demi-glace recipe presented by Le Cordon Bleu. About.com's recipe requires purchased or pre-prepared espagnole sauce and stock, while Le Cordon Bleu's recipe provides instructions for making demi-glace without using a pre-prepared sauce.
For About.com's simple demi-glace recipe, combine 2 cups of espagnole and 2 cups of brown stock in a saucepan. Bring the mixture to boil over medium heat, then bring the temperature down to a simmer. If desired, add a spice sachet made of 1 bay leaf, 1/2 teaspoon of dried thyme and 3 to 4 fresh parsley stems.
Simmer the mixture for approximately 45 minutes, or until it has reduced by half. Remove the saucepan from the heat, and remove and discard the spice sachet. Pour the demi-glace through a wire mesh strainer lined with cheesecloth. This recipe makes 1 pint of demi-glace.
To make Le Cordon Bleu's demi-glace recipe, add 2 cups of beef or veal stock to a saucepan. Add 1 cup of red wine, preferably burgundy, as well as 2 tablespoons of chopped shallot, 2 teaspoons of fresh, chopped thyme, 1 teaspoon whole peppercorns and 1 bay leaf. Simmer the mixture until it reduces by half. The demi-glace evenly coats the back of a spoon when it reaches the proper consistency.
When the sauce reaches the correct consistency, remove the pan from the heat. Stir in 2 tablespoons of butter until completely melted and combined with the sauce.