Asian chile sauce; chile paste; Thai chile paste
Asian chile pastes are hot sauces made primarily from ground chiles, oil or vinegar, and salt. They may also include other flavors, such as garlic, ginger, sugar, sesame, black beans, or soybeans. Unlike most of the thin, smooth, chile-based hot sauces of the Americas, Asian chile pastes tend to be coarse and on the thick side, full of bits of ground chiles and sometimes whole seeds.
Though they won't provide the full flavor spectrum of most chile pastes, you can use hot sauce or red chile flakes to add some heat (use less than the amount of chile paste called for).
You'll find the broadest variety of chile pastes at an Asian grocery store. Be sure the first ingredient listed is chiles. Chile pastes aren't usually labeled as to their heat intensity, so experiment to find a brand you like. A few of our favorites are Lan Chi brand in glass jars, Szechwan brand in cans (both are Chinese), and Indonesian-style sambal oelek by Huy Fong Foods in plastic jars.
Use right out of the can or jar at the beginning of cooking if you want it to really permeate the dish, or at the end if you want more of a surface heat.
Some pastes separate during storage, so stir them before using. Once opened, chile pastes will last indefinitely if tightly covered and refrigerated. Transfer canned paste to a jar before storing because the metal can get unpleasant.