Put the shank in a large saucepan, add the water and bring slowly to the boil, skimming off any scum. Add the onion, bouquet garni, some salt, the peppercorns and celery, and simmer uncovered for 2 hours, skimming as you go.
Meanwhile, prepare the stuffing. Soak the bread crumbs in the milk to moisten, then squeeze dry. Mix them with the gammon, garlic and parsley. Chop the chicken liver and heart, and add to the mixture with the beaten egg. Season with pepper and nutmeg (you may not need salt, but taste to see). Beat very well until thoroughly mixed. Stuff the bird and truss it. Add the bird to the pot with the shank and continue to simmer uncovered for 1 hour. Add the carrots, leeks, and turnips. Taste for seasoning, then continue to simmer for another hour or until everything is tender. Be sure that there is always enough liquid to cover everything.
If you are going to serve the broth as a first course, strain 2 1/2 pints of the liquid into a separate pan, boil to reduce by one-third, remove as much fat as possible and adjust the seasoning. Either simmer the noodles in it for 5 minutes or serve with the diagonally sliced French bread - toasted in a preheated 350 degree oven for 10 to 15 minutes. (Put the slices of bread in soup bowls and then pour the broth over them.)
Transfer the beef and chicken to a board. Meanwhile, cut the shank into medium-thick slices and arrange on a large platter. Untruss and carve the chicken. Pile the stuffing on the platter and arrange the chicken on top. Put the vegetables in pretty array around the meat. Cover and keep hot while you serve the first course.
Serve the meat platter as the main course - it may need some coarse salt to go with it.