French black truffles are most definitely not a supermarket item, and I have therefore made their use optional. Truffles are fungi that grow underground and are prized for their unique flavor. They can range in size from ยฝ inch in diameter to as large as 2 to 3 inches, and in their fresh form are usually found only in a few high-end specialty stores and expensive restaurants. I call for medium-size truffles, which measure about ยพ inch in diameter, packed in cans or jars.