In the 900 years of history between the medieval Emilian monks’ Parmigiano Reggiano (Parmesan Cheese) and today's master parmesan-makers, very few things have changed. Using just local milk and natural rennet, producers allow from 18 to over 30 months for aging, while a consortium carefully certifies the attributes of every single wheel: year of production, time of aging and quality. There are many parameters that a connoisseur has to consider in order to recognise quality. The greatest trick? Use the senses, never use a knife: Parmesan has to be cracked in order to maintain its distinctive texture.