Up there with caviar, foie gras and champagne as one of the world's ultimate luxury foods, oysters don't look much from the outside (the shells are rough and grey), but the flesh of these bivalved molluscs is wonderfully succulent and delicately flavoured, varying in colour from pale grey to beige, surrounded by a clear juice.
In Britain, the two main types available are Natives (grown in Whitstable, Colchester and Helford) and the less expensive Pacific (also known as rock or Gigas), which has a larger, longer shell.
In Ireland, the best native oysters are considered to come from Galway. You can also buy frozen oysters and tinned smoked oysters.
During the summer months they're busy spawning, and their flesh becomes unpleasantly soft and milky. Rock oysters are available all year round.
Choose the best
Live, just-shucked (ie just-opened) oysters have the best flavour. If you don't want to shuck them yourself, you can ask your fishmonger to do it for you, but you'll need to eat them as soon as possible after that.
Although they tend to be smaller than rock oysters, natives are thought to taste superior - more complex, with a faint metallic note. They are graded by size, from 1 (the largest) to 5 and grow very slowly (they take three years to reach full size). They are more expensive than rock and tend to be eaten as simply as possible, so that their taste can be enjoyed to the full.
Rock oysters have a sweeter, salty, more unctuous flavour. Their larger size, and the fact that they're less of a strain on the wallet, means they're good for cooking with, as well as eating raw.
Scrub the live oyster shells with a stiff brush under cold running water, and discard any that are cracked or damaged. Any shells that aren't tightly closed, or whose open shells do not snap shut when tapped should also be thrown away, as the oyster inside is dead.
To shuck an oyster, wrap a teatowel thickly around your hand to protect it, then grip the oyster in the same hand, with the cupped shell down in the palm of your hand and the hinge pointing towards you. Insert a shucking knife (or, if you haven't got one, a short knife with a sharp, strong blade) into the small gap in the hinge and twist it from side to side until the hinge breaks. Lever open the top (shallower half of the) shell, then run the knife gently along the inner edges of the top shell to free the oyster. Discard this shell. Using the knife, gently free the oyster from the muscle that binds it to the deep shell, to leave the oyster sitting in its juices. Pick out any fragments of broken shell with the tip of the knife, but try not to spill any of the juice.
Frozen oysters should be defrosted for at least four hours in the fridge, then eaten straight away.
Cover live oysters with a damp teatowel and put in the fridge with the larger side down. They will keep up to three days, but the sooner you eat them, the better they'll taste. Shucked oysters should be kept covered in the fridge, and eaten on the same day as purchase.
Arrange them on a bed of ice and serve raw, just as they are, or with lemon juice, a French-style shallot vinegar, one or two drops of Tabasco or mirin (Japanese rice wine).
Top with breadcrumbs, herbs, and grated parmesan and grill (2-3 minutes); pan-fry, poach or steam (2-3 minutes).
Bake in a traditional Irish steak and oyster pie. Use to make angels on horseback (wrap in bacon, pancetta or Parma ham and roast (6 minutes).
Try mussel or cockle.