Parmesan is a straw-coloured hard cheese with a natural yellow rind and rich, fruity flavour. It is made from skimmed or partially skimmed cow's milk. Italy's 'Parmigiano Reggiano' is the original parmesan, although similar versions can now be found from Argentina, Australia and the USA.

The original Italian version remains superior however, boasting a ripe yellow interior, granular texture and unbeatable flavour. This is partly due to a longer maturing time of around two years, rather than the minimum 12 months required. Authentic Italian parmesan has 'Parmigiano Reggiano' stamped on the rind.

Parmesan swiftly loses its flavour when it's grated, so try to avoid buying it ready-grated in tubs or bags, as it will bear no relation to how it should really taste. Always buy Parmesan in a chunk, from which you can cut at home as needed and, if possible, buy it from a place where you can see the piece being cut from the whole cheese.

Parmesan is sold at various stages of the maturing process. Giovane is the youngest (14-18 months); Vecchio is 18 months to 2 years; Stravecchio is 2 or 3 years old and the extra mature Stravecchione is 3 to 4 years old. The more mature the cheese is, the more expensive; younger cheeses are more economical to cook with, while the deeper flavour of older parmesan is best appreciated when eaten as a dessert cheese.

As with all cheeses, buy little and often, so that the cheese is always at its best.Keep wrapped in greaseproof paper inside a polythene bag, and store in the fridge - that way it should keep for around two months. Don't wrap it in clingfilm, as it will make it sweat, but foil is acceptable in the absence of greaseproof. If the cheese develops some mould on the surface, just scrape it off; the cheese underneath should still be good to eat.

BBC Good Food Glossary