Clean the tongue by blanching about 5 minutes. Remove coarse outer layer.
Fry the tongue to seal the meat.
In a large pan, cook the tongue with the peppercorns, bay leaf, salt, vinegar, gin and onion.
Bring to a boil then simmer covered. As the liquid reduces, add water until the tongue is cooked.
Remove the tongue and strain the remaining stock back into the pan. Reserve the stock.
Slice the tongue diagonally into 1/4-inch portions and set aside.