Tempeh is a fermented food product, most commonly made with soybeans, although other ingredients such as whole grains and other beans are sometimes used. The idea of making tempeh originated in Indonesia, where it is a staple food, and several other Southeast Asian countries have adopted tempeh as well. In the West, a growing number of cooks are experimenting with tempeh, along with other soy foods, and it is readily available in many markets in both fresh and frozen forms. Fresh tempeh can also be frozen, if it is not going to be used within a few days, and experimental cooks can also make tempeh at home.

When selecting tempeh to eat, look for a solid cake with a whitish bloom. Black flecks or veining are also acceptable, but any other color suggests that the tempeh may have gone bad. In addition, slimy tempeh is not good to eat, along with tempeh which smells strongly of ammonia. Bad tempeh does not just taste bad; it can also cause regrettable gastrointestinal experiences. Good tempeh has a slightly nutty, musty aroma and flavor.

When making traditional tempeh, cooks start by blanching and peeling soybeans. The partially cooked soybeans are mixed with a fungus, Rhizopus oligosporus, and allowed to ferment. The result is a dense cake, high in protein and low in fat, with a white moldy bloom. If actual mold appears, it is cut off before cooking. Unlike other soy products, tempeh is very easy to digest, because the fermentation breaks down the structures which make soy difficult for the body to process. In addition, the chemical which causes gassiness after eating beans is also broken down.

In traditional Indonesian cooking, tempeh is used in a variety of foods. Vegetarians around the world also use tempeh as a meat facsimile, and it appears in veggie burgers, stir fries, and vegetarian breakfast foods. Like other soy products, the flavor of tempeh is relatively bland unless it is fermented or flavored with other foods, and it readily takes on flavors it is cooked in. For this reason, highly absorbent tempeh is favored by some vegetarian cooks for stir fries and similar dishes.

In addition to being sliced thin or diced into chunks for stir fry, tempeh can also be grilled, baked, or broiled. The dense chewy cake holds its shape very well unless it is manually cut or crumbled, and it takes well to marinades and dressing. As well as being served hot, tempeh can also be used cold for sandwiches and box lunches, as long as it is quickly chilled after cooking so that harmful organisms are not encouraged to grow on it.