Tongue is very tasty but takes a long time to cook.
Wash the tongue(s) carefully. Add hot water and bring to a boil. Remove the foam that accumulates on top.
Peel garlic cloves and onions, then slice them thinly. Wash herbs and chop them finely. Add garlic, onions, and herbs to tongue and cook over low heat for 4-5 hours, adding more hot water during cooking if necessary. Salt and black pepper should be added near the end of cooking. When tongue is cooked, there should be about one cup of water left. Remove tongue and peel the skin while still warm. Allow to cool, then cut into thin slices using a sharp knife.
Wash and slice mushrooms, then fry in butter for a few minutes. Add tomato paste and tongue-juice and bring to a boil, then cook over medium heat for a few minutes. Serve tongue with mushrooms and some fresh parsley. If desired, pooreh-yeh Seeb-Zamini or Polow can also be served with tongue.