Put the meat in a large pot and pour over the broth or water to cover. Bring to a gentle simmer and skim oft any scum that floats to the top. Simmer gently for about 2 hours, regularly skimming off and discarding fat. Add the vegetables and bouquet garni and simmer for 1 hour more. Lift the meat out of the broth and slice. Serve some of each kind of meat on heated plates and spoon some of the broth around the slices or reserve it all for another use. Pass the mustard, cornichons, salt, and pepper at the table. Keeps for up to 5 days in the refrigerator.