The concoction that lends its name to ngo hiang (which means five fragrances in Hokkien), is gound from star anise, cassia bark, fennel, cloves and Sichuan peppercorns.
Sometimes, there might be two additional spices, from coriander, ginger, dried orange peel or cardamom. As a result, each source of five-spice powder is unique based on the basic ingredients and the proportion used. Stick with one that you personally like and which is not too overpowering. The fresher and higher quality powders can be found in Chinese medicinal shops.