To clean tongue, dip in 3 cups boiling water. Let stand for 5 minutes, then scrape white, thick skin. Then wash in clear water.
Place in deep pan, pour water enough to cover tongue. Boil. Lower heat and simmer until half done.
Saute onion and pork fat (in big slices) in butter. When onion is wilted, add all ingredients except bread crumbs.
Stir for 3 minutes, then add to the deep pan where you boil the ox tongue. Continue cooking until the tongue becomes tender.
You may add more water if sauce dries and meat is not yet done.
Let it cool. Cut tongue into thin slices. Arrange in serving plate. Thicken sauce with bread crumbs then pour over sliced tongue.