Place chicken in a large pan, add water, peppercorns, ginger, onion and parsley. Bring to boil, reduce heat and simmer covered for 1 1/2 hours. Skim to remove any scum. Strain and reserve 6 cups stock. Remove meat from chicken, shred finely. You will need about 1 1/2 cups finely shredded meat for the soup, reserve the rest for another meal.
Combine chicken stock, corn, stock cubes, extra ginger, shallots and sesame oil in a large pan, bring to the boil. Combine cornflour with 4 tablespoons cold water and add to soup, stirring until it has boiled and thickened, about a minute.
Lightly beat egg whites with 2 tablespoons of water and add to soup in a thin stream, stirring well.
Add ham and shredded chicken to soup and heat thorugh gently.
Serve garnished with spring onions and pass soy sauce separtely, for a dash of flavour (if desired).