Soak the oysters in warm water for 2 hours and clean them thoroughly. Soak the mushrooms in warm water for 15 minutes and remove the stalks. Cut the pork and bamboo shoots in pieces 1 inch long and ½ an inch wide. Crush 1 clove of garlic with a knife and put it in a hot oiled pan for 2 or 3 seconds. Remove, and put the mushrooms in the pan and cook for 5 minutes. Then add the oysters, roast pork, bamboo shoots and fry all together for ½ a minute. Remove from the pan and put all in a saucepan with sufficient stock to cover. Bring to the boil and simmer for 4 hours. Add peaflour water, a few drops of Chinese sauce, and salt and pepper to taste.