This is a classical French brown sauce, also called sauce espagnole. It is the basis for many other sauces. The secret is to use good quality, strong beef stock and to simmer the sauce very slowly. It freezes well.

1/2 cup diced carrots
1/2 cup diced onion
1/2 cup diced celery
4 tablespoons diced lean bacon, blanched and drained
4 tablespoons clarified butter
4 tablespoons flour
8 cups beef stock, boiling
3 tablespoons tomato paste
4 large sprigs parsley
1 bay leaf
1/2 teaspoon thyme
Salt, to taste
Freshly-ground pepper, to taste

In a heavy 2-quart saucepan, saut