The commercially prepared powdered spice known as chili powder is actually a blend of ingredients, including powders from dried hot peppers, dried garlic, finely ground dried oregano, cumin, and salt.

Depending on the brand, chili powders can be made from ancho chilies, cayenne chilies, pasilla chilies, or virtually any other hot pepper. They may also include small amounts of many other spices such as cinnamon, cloves, mace, and onion powder. This is why different brands often taste very different from one another.

Chili purists compose their own chili blends or make sauces using fresh roasted or reconstituted and puréed dried peppers, along with their own preferred quantities of ingredients like cumin and garlic.

Increasingly, single-source chili powders have become available in supermarkets. Like cayenne, these peppery powders usually don't have extra ingredients, so you're getting a pure dose of chipotle chili, New Mexico chili, or ancho chili. If your favorite store doesn't stock single-source powders, try a Mexican food market or order online directly from pepper growers.

Asian chili preparations usually take the form of pastes rather than powders. This is because perishable ingredients like lemongrass, galangal root, and Kaffir lime leaves are essential to the flavor of Southeast Asian dishes. These can't easily be powdered, hence the shelf-stable pastes.

You can purchase hot Thai chilies or an equivalent chili pepper at many venues, but to get the full from-scratch experience, you'll have to track down an excellent Asian market that handles a range of perishable goods. For convenience, you may want to start by experimenting with different pastes.