my mother makes this dish often too when I was growing up. I in addition to the recipe of soya sauce, rock sugar, water, and five spices, she puts in crushed cloves of garlic, shredded ginger, star anaise and add a thick sweet black sauce to taste.(from red dates, you might be able to find it in the Chinese provision store, I managed to find it in the store when I was living in Italy). Also, my mother used to always say the stomach has to be thoroughly marinated otherwise it would smell, so she would put it in a pot of marinate of all the above ingredients. I can only guess the spice is from the shredded ginger and perhaps some ground pepper.
