In a heavy saucepan, melt drippings or butter. Add onions and carrot and cook them, shaking the pan to insure even cooking until onions begin to turn golden. Add flour and cook the mixture over low heat, stirring, until the flour-onion-carrot mix is a rich brown. Remove the pan from the heat and add 3 cups of heated stock, stirring the mixture until it is well combined. Add parsley, celery,bay leaf, garlic clove,thyme and cook mixture over low heat, stirring frequently, until it thickens. Add 3 more cups of stock and simmer the sauce, stirring occasionally and skimming the froth as it rises to the surface for 1 to 1 1/2 hours or until it is reduced to about 3 cups. Add tomato puree and cook the sauce 5 more minutes. Strain it through a fine sieve into a bowl. Return the sauce to a pan, add 2 more cups of stock and continue to simmer the sauce, skimming the froth , until it is reduced to about 4 cups. Strain the sauce and let it cool.

Refrigerate to use later or as a base for other sauces.