To Make Soup: Place chicken in soup pot with enough water to cover. Bring to a boil, reduce heat, and skim foam as it rises to the surface. When it has subsided, add onion, peppercorns, salt, and saffron. Simmer gently but steadily, partly covered, for about 1-1/2 hours or until tender. Remove chicken. Trim and discard bones and skin, and onion. Let soup cool, then skim fat from surface. Tear meat into spoonable pieces and return to soup. Cut kernels from 4 ears of corn, then grate kernels from remaining 4 ears using the large side of a box grater, catching all milk and pulp in a large bowl. If using frozen kernels, puree half in a food processor or blender, adding a little soup if liquid is needed. Add whole kernels and grated or pureed corn to soup along with celery and noodles, egg barley, or rivels. Simmer gently until corn and noodles or rivels are cooked. Add salt and pepper to taste. Stir in parsley and serve, garnishing each portion with chopped hard-cooked egg. This soup freezes well, but do that before adding the noodles, barley, or dumplings. Prepare those when reheating soup. To Make Rivels: Stir salt and pepper into egg and add 2/3 cup flour and beat. Keep adding and beating in flour until mixture is crumbly but a bit sticky. Rub between hands or pinch off pea-size pieces and drop them into simmering soup. Cover loosely and let cook for about 15 minutes or until rivels solidify. To make the rivels ahead of time, cook them in lightly salted boiling water or some extra soup stock and then drain and reserve them to be reheated in the soup just before it is served.