Melt the butter in a heavy saucepan over medium heat. Add the carrot, celery, and onions and saute until golden, taking care not to let them brown. All at once, stir in the flour, and turn the heat down to low. Cook, stirring occasionally, until the flour and vegetables are well browned, but not burned. Stir in the stock, then add the garlic, bouquet garni and tomato puree. Simmer for 1 Hour, stirring from time to time, or until the sauce is reduced by half. Strain. Allow to cool, then chill and skim off any fat before using.
While this very basic sauce is excellent by itself over beef, noodles, and some game, such as venison and bear, it is generally used as a base for other more complex sauces. It may seem very time consuming to make a brown stock, then this basic brown sauce and then a finished sauce, but the result is well worth the effort. Both the stock and this sauce can be frozen for up to three months, which means you can make your own instant bases to have on reserve, which will speed up the process.
Yield: About 3 cups
From The Complete Book Of Sauces by Sallie Y. Williams