Truffles are one of the most expensive (and revered) cooking ingredients – "kings of the edible fungi," as Italian food authority Valentina Harris describes them. The white truffles of Alba and the black truffles of Périgord are perhaps the best-known varieties. Available in the fall, they are definitely worth seeking out, and a little goes a long way in dishes such as Shaved Truffle Pizza and Grilled Scallops with Truffle Butter.