The secret is to use wu-hua jou [pork rib meat] as they do in Chenchiang. It's a little fat, but they stew it over low heat for several hours to remove the lard so it doesn't feel greasy when you eat it.
主要在鎮江人用五花肉，雖然肥一些，但文火燉幾小時，油已經出盡，所以吃的人不覺得膩。