Start with the chicken stock in a pan and add the ginger, spring onions and peppercorns.
Bring the contents of the pan to a boil and cook for 20 minutes for the flavours to infuse before straining the liquid.
While the broth cools, chop the sweetcorn cobs on a board and slice off the kernels with a large sharp knife.
Pour the sweetcorn into the stock mixture and simmer for five minutes.
Scour the crab meat for shell fragments, keeping the meat in the largest pieces possible.
Mix the cornflour to a smooth paste with a little cold water, stir it into the soup and simmer for two minutes.
Add the crab meat, ginger, spring onions, soy sauce and the rice wine or sherry, then season the soup with salt and some pepper to taste.
Simmer for one minute.
Stir the soup, remove the spoon, and slowly trickle in the beaten egg white until it forms long, thin strands in the soup.
Simmer everything for about 30 seconds before serving.
