Brine all the meat overnight. Drain and rinse the meat. Add the meat and stock ingredients to a 20 quart stockpot and add water to cover as much as possible. Bring everything to a boil and maintain a very slow simmer for 3-4 hours, skimming fat as needed, until the stock is very dark. Remove the meat and let it cool. Bring the remaining stock to a rolling boil until it reduces in volume by 1/3, about 2 more hours. Meanwhile, pick off the edible meat from the tongues, head, and trotters. The tongues must be peeled. Work around the bones and skin, judiciously selecting the meat and a little of the fat. The meat should fill one terrine, lined with plastic wrap, with some leftovers. Mix the meat with the parsley or other flavorings. Ladle the reduced stock over the meat to fill the terrine, then salt the entire thing to taste. Cover and refrigerate the head cheese overnight or until set. The terrine should be firm all around. Invert onto a serving plate, remove the plastic wrap, and serve with salsa verde, cornichons and other pickled accompaniments, mustards, bread and a salad.