To brown the bones, put them in a shallow pan in a hot oven, and cook until they have taken on a good, brown color.
Prepare stock by cooking browned bones.
Melt fat; add onion and carrot, and cook until golden brown.
Add flour and cook until a good deep brown.
Add stock and tomatoes and boil, stirring constantly, until flour and fat are combined with the liquid.
Add celery, parsley, herbs, garlic, salt and peppercorns; and cook gently, skimming when necessary, for about 2 hours, when there should be about 2 cups of sauce left.
Strain, let cool, and use as needed.
This sauce is marvelous added to stews, leftover dishes and to other sauces.
It thickens them, and gives full rich flavor.
After sauce cools, it can be frozen in ice cube trays.
When frozen, cubes can be stored in plastic bag in freezer, and a few cubes used in cooking as needed.