No other food has developed quite the same mystique as this knobby, aromatic underground fungus. Until now, it has been impossible to cultivate, so finding it has traditionally been a matter of having a good truffle dog or pig who could smell a truffle buried in the earth under oak trees in Europe. The two most valuable kinds of truffle are the black truffle (sometimes called "black gold") of France, particularly from the Périgord and Quercy areas, and from Umbria in Italy; and the white truffle of the Piedmont region in Italy.

Truffles have a strong, earthy aroma and are used to flavor a variety of foods. The white truffle is even more powerfully scented than the black, although its flavor is somewhat milder. Black truffles may be cut into very thin slices or matchsticks and added to pâtés and terrines, and they are often used to flavor foie gras. Minced or shaved black truffles are used as a counterpoint to mild foods, such as eggs, and are added to sauces for meats and poultry for rich flavor. White truffles are used raw, grated or shaved, over cooked pasta, polenta or risotto.

Selecting
Truffle season begins in late autumn and lasts through the winter. Look for fresh truffles in specialty-food stores. A single truffle is usually packed on a bed of rice in a glass jar. The rice absorbs moisture and keeps the truffle from spoiling. (Be sure to cook the rice, which will have taken on the flavor of the truffle.) Whole, minced or sliced truffles are available in jars or cans year-round, as are truffle paste in tubes and truffle oil in bottles. Truffle oil is an especially good way to add the truffle's haunting fragrance to pasta dishes, salads and main courses. Sprinkle it on hot foods just before serving to preserve the truffle flavor.

Storing
Keep a fresh truffle, in its jar of rice, in the refrigerator, but use within a few days of purchase, or the truffle will dry out and lose fragrance. Canned and jarred truffles, truffle paste and truffle oil will keep indefinitely in a cool, dark place. Refrigerate them after opening.

Preparing
Brush fresh truffles clean with a soft mushroom brush or damp kitchen towel. Peel black truffles, saving the peel to flavor other dishes or to infuse olive oil, but use white truffles unpeeled. Grate truffles on a grater, or cut them into paper-thin slices, or shavings, with a vegetable peeler, a mandoline or a tool called a truffle slicer. Slices of black truffles may be used whole or minced with a chef's knife.

To scent eggs with a truffle, remove it from its jar and bury it in a bowl of eggs in their shells. Cover and refrigerate for 2 to 3 days. Then prepare luxurious scrambled eggs.

Adapted from Williams-Sonoma Kitchen Companion: The A to Z Guide to Everyday Cooking, Equipment and Ingredients (Time-Life Books, 2000)