Duck soup with purslane and ginger

1. Start to make this soup the day before you plan to serve it. Put the duckling in a pan with the cold water.
2. Add the halved onion, sliced carrot and celery, bay leaf and parsley.
3. Pick the tips off the purslane or watercress, set them aside and add the stalks to the pan. Throw in some salt and 8 or 9 black peppercorns.
4. Bring to a boil and simmer gently for 1 hour.
5. Or a little longer.
6. Until the duckling is just cooked.
7. Lift it out and cut off the best meat.
8. Wrap the meat in cling film (saran wrap) and set aside.
9. Return the carcass to the pan. Continue to cook for another hour, adding more water if necessary.
10. Straini the liquid and discard the vegetables.
11. Leave the soup to cool before putting it in the refrigerator.
12. The next day, remove all fat from the surface and taste the soup.
13. If the flavour is too weak, reduce the quantity of liquid by fast boiling.
14. If the flavour is satisfactory, reheat the soup in a clean pan, adding the roughly chopped purslane (or watercress) tips, the sliced root giner, the diced meat of the bird, and more salt and pepper as needed.
15. Stiri in the vinegar and the chopped chives and serve.
16. If you do not have any tarragon or dill vinegar, substitute a tablespoonful of each of lemon juice and white wine vinegar.
17. A cheaper version of this soup can be made using a joint of duck and some chicken wings.