The document discusses the black winter truffle (Tuber melanosporum), one of the most expensive edible mushrooms. It grows symbiotically on the roots of oak and hazelnut trees in parts of Europe. Historically, 1,500-2,000 tons were harvested annually in Europe, but production has declined significantly. Black truffles are usually found using trained dogs and have a distinctive black rounded shape covered in diamond markings. The document also provides details on cultivating black truffles commercially and includes a recipe for a truffle omelette.