Shark's Fin Soup

1. Put the shark's fin in a large container and pour over about 1.4 litres hot water. Soak overnight or for a minimum of 6 hours.

2. Rub with fingers. Drain through a fine sieve so as not to lose any of the precious shark's fin needles while getting rid of fine sand. Repeat as many times as necessary. Put into a large saucepan.

3. Add about 1.7 litres water. Bring to the boil and simmer gently for about 2 hours, replenishing the water if it evaporates too quickly.

4. Test if the fin needles are ready: they should be tender yet still firm. Another way of testing is to press one between the thumb and the index finger: if it breaks easily, it is ready. Drain. If the fin is still hard, let the water cool, then drain. Return to the saucepan, add the same amount of water and boil gently for another oil or longer. Drain, taking care not to lose the needles.

5. Meanwhile, cut the chicken flesh into matchstick-sized pieces. Put into a small bowl.

6. Prepare the marinade: add the salt, sugar, pepper, wine or sherry and cornflour to the chicken. Stir in the egg white in the same direction and leave to marinate for 20-30 minutes. Blend in the oil.

7. Place about 1 litre water in a saucepan with the ginger, spring onions, half the lard and 2 tbsp of the wine or sherry. Bring to the boil. Add the shark's fin and boil gently for about 15 minutes. This curing process rids the fin of any remaining rank odour. Drain, discarding the ginger and spring onion.

8. Cut the ham into matchstick-sized pieces.

9. Pluck and discard the bean heads off the bean sprouts. Blanch in boiling water until the water returns to the boil. Drain, then refresh under cold running water. Drain thoroughly.

10. Arrange the ham and bean sprouts in bunches on 1 or 2 small serving dishes. Put the vinegar and mustard into separate saucers on the dining table.

11. Prepare the sauce: mix the flour, water and soy sauce thoroughly.

12. Heat a wok or saucepan over a high heat until hot. Splash in the remaining wine or sherry. As it sizzles, add the remaining lard and the oil. Pour in the prime stock, add the shark's fin and stir to mix. Slowly bring to the boil, then add the chicken, stirring to separate the pieces. Reduce the heat. Gradually add the well-stirred sauce to the soup, stirring as the soup thickens. Remove from the heat. Taste for seasoning, add salt and thin soy sauce, if necessary.

13. Transfer to a warm soup tureen and serve. To eat, each person puts some bean sprouts and ham into the bowl before adding the shark's fin soup. Some may also like to add a little vinegar or mustard to the soup.