Place the tongue in a large pot and cover with water. Bring to a boil, reduce the flame, and simmer until the tongue is tender, about two and a half hours (depending on size).

Transfer the tongue to a large plate and let it cool just enough that you can handle it. (It’s easiest to peel when it’s still hot). Reserve two cups cooking liquid and set aside. 

Slit the skin on the underside from the thick end to the tip, then loosen the skin all around the thick end and pull it off. (If you put on a pair of gloves, it’s not that bad — just don’t think about what you’re holding!) With a sharp knife, trim all the bones and gristle from the thick end of the tongue. Cut the tongue crosswise into thin slices. Set aside.

In a large saucepot, mix together the onion, potato starch, cooking liquid, tomato sauce, sugar, lemon juice, and wine. Bring to a boil.

Add the tongue slices. Reduce the flame and simmer for 15 minutes. 

Remove and discard the onion pieces. Serve the tongue slices on a platter. Decorate with sliced or slivered toasted almonds.