Preparation: In bowl, thoroughly mix pork, water chestnuts, ginger root, green onions, cooked rice, dark soy, sesame oil & water. Allow mixture to marry for 30 minutes. Form into firm balls, one for each serving, each the size of a tennis ball (about 9 cm across). Braising: Heat wok or skillet to hot; add oil. When oil begins to smoke, introduce meatballs 1 at a time, so as not to cool oil. Fry meatballs until a brown crust has formed. They must be well crusted in order to retain their shape while stewing. Cooking in Sandy Pot: Line sandy pot with shredded Chinese mustard cabbage; sprinkle with pan oil from meatballs, salt & sugar. Add meatballs, then add cool or cold stock. Bring slowly to boil; cover; reduce heat to medium & simmer for about 2 hours. Correct seasoning if necessary. Serve.