In the culinary arts, five spice (also known as Chinese five spice) is a blend of ground spices used in Chinese and Vietnamese cooking.
One theory behind the composition of five spice powder is that it is intended to incorporate the five main flavors of sweet, sour, salty, bitter and pungent. In truth, there is nothing salty in the traditional five-spice blend. Also, in the culinary arts, pungent (or spicy) is not typically considered a flavor in its own right. Still, the theory that five spice encompasses a balance of the main flavors, in accordance with the balancing philosophy of yin and yang, is widely cited.
Chinese five spice can be used for seasoning meats and poultry, in marinades or in spice rubs. Because it is also sweet and aromatic, five spice can be used in flavoring desserts as well as savory dishes.
Make Your Own
You could blend your own five spice by grinding the spices yourself in a spice grinder or coffee grinder. Unfortunately, Szechuan pepper is not widely available, although it can be found in specialty spice shops or Asian markets. Also, the Szechuan peppers need to be toasted first, which adds another step to the process. Moreover, most stores sell bottled five spice powder, so it's really not necessary to make your own, especially if you won't be using very much of it.
The thing to remember with five spice powder is that its potency diminishes rapidly once the spices are ground. Thus, your five-spice powder (and indeed all ground spices) should be stored in an airtight container and away from heat (i.e., not near the stove).