Cut the fresh ham into several chunks about 1.5 to 5 cm square. Chop the green onion fine. Heat the oil in 2 litre pot, then add the onion and the remaining ingredients, including the pork. Saute, stirring, on medium heat until the meat is brown (about 5 minutes or more). Add 4 cups water and simmer, uncovered, on medium heat for one hour. Add the fish sauce and continue to simmer on medium heat 1 more hour. Most of the water will be absorbed by the meat and the remainder will be slightly thick--or carmelized. Be careful not to burn it. Serve hot as a main dish, with lots of rice. This has a very long life--it may be frozen, refrigerated, reheated, and served as an appetizer, etc. Note: This takes a long time to cook, but is very easy to do. In Hue, central Vietnam, pork belly is used in this recipe. Bellyis very fat and is considered good in a cooler climate. Don't discard the fat portions before tasting--it is surprisingly good and surprisingly digestible. Recipe from: Vietnamese Cookery, by Jill Nhu Huong Miller.