For 2 cups of sauce
At this point, lower the heat, add 1 oz of rich mirepoix (5,2 oz of carrot, 3,5 oz of onion, 2 oz of celery and 3,5 oz of fat and lean dry-cured ham seasoned with salt, thyme and bay leaf, and cooked in a little butter) and leave to cook, over moderate heat, for 2 hours, skimming frequently and adding, from time to time, some spoonfuls of brown stock.
Finely filter the sauce into another casserole gently squashing the mirepoix, mix in an equal quantity of brown stock and leave to cook for a further 3 hours, over very moderate heat, skimming often.
Pass through a canvas sieve and, while cooling, continue to mix frequently to avoid a film forming on the surface.
Spanish Sauce can also be low-fat if made with low-fat mirepoix (without ham), consisting only of vegetables, and in this case is usually used for fish.