This star-shaped spice is the dried fruit of a small Asian evergreen tree (a member of the magnolia family). Harvested when it's still green and unripe, it's dried in the sun, where it develops its red-brown color and a sweet warm flavor that's reminiscent of licorice, clove, fennel seed, and aniseed (although it's botanically unrelated to any of these spices).
Star anise is used primarily in Vietnamese and Chinese cooking. Much like bay leaves are used in Western cuisines, whole stars are used to infuse soups, stews, and braised dishes. Ground star anise is a dominant ingredient in Chinese five-spice powder.
A little star anise goes a long way; try adding a pinch to a stir-fry or adding it to the liquid for poaching pears or other fruit.
Substitute aniseed for ground star anise, but use about twice as much.
Some supermarkets carry whole or ground star anise, but your best bets for the freshest spice are Asian markets, natural food stores, and mail-order spice houses.
If you need ground star anise, you can grind the whole stars (both seed and pod) in a spice grinder or mortar and pestle.
Like all spices, star anise should be stored in an airtight container away from heat and light. Whole stars will stay fresh for about two years; ground star anise lasts about one year. To check the freshness of a whole star, break off a point and squeeze it until the seed pops. If you don't immediately smell the distinctive aroma, it's past its prime.