Gorgonzola PDO is Italy's great blue, made from cow's milk only in defined provinces of Piedmont and Lombardy and aged in cool cellars until it turns creamy and blue-green. It comes in two styles — the milder dolce and the firmer, sharper piccante.
The imitation is any anonymous ‘Italian-style blue’ made outside the zone. The PDO mark and its consortium foil guarantee the genuine article.