There are thousands of different species of prawn, but tiger, king and North Atlantic are the most commonly sold in the UK. They are fished in both the ocean and fresh water, and are farmed as well as wild.
Most of them have a narrow, tapering body, under which the tail is curled, and long, whiskery antennae. The body is encased in a brittle shell, and all types have ten legs. When raw, they are bluey-grey or, in the case of the smaller varieties, almost translucent.
When cooked, the shells turn pink and the sweet, meaty flesh turns white tinged with pink; brief cooking is essential, otherwise the flesh will become tough. As with other types of crustacea, prawns fished in cold waters tend to be more flavourful than those from warm waters. Although anatomically incorrect, the part of the prawn eaten, the meaty body, is referred to as the tail. The very small shellfish referred to as shrimps are prawns, too - the term shrimp just indicates their diminuitive size.
Choose the best
Fresh prawns, whether raw or cooked, should smell fresh and clean, not fishy, and should look moist. Avoid any that look dry or that have broken or cracked shells.
If you are buying shell-on prawns, buy double the weight that you would need of shell-off prawns.
Prawns can be bought raw or cooked. They can be used in the same way and in the same kind of dishes, though cooked prawns can be eaten cold as they are. When raw, they are blue-grey in colour (and are sometimes called green prawns).
Tiger or king prawns, which are big and juicy, are the types most commonly sold raw, either whole in their shells, or with their heads removed (if the latter, they are called prawn tails). The North Atlantic prawns are smaller and are also sold raw, usually whole.
When cooked, prawns turn pink. Tiger and king prawns are both available cooked, often with their heads and shells (aside from the very end of the shell) removed. North Atlantic prawns are also sold cooked, either whole or headless; if headless, they tend to be shells-off, too (aside from the very end of the shell).
You can find pink and brown varieties of shrimp, and they are sold ready cooked. Ready-peeled ones are the best to go for, as it's a fiddly job to do.
If the prawns are shell-on, you'll need to peel them. This can be done before or after cooking, but peeling them after cooking makes for a juicier, more flavourful prawn.
Grip the body of the prawn in one hand and twist the head off with the other (this can be used to make stock). Turn the prawn over and pull the shell open along the length of the belly, working from the head end downwards, prising it open so that you can pull the prawn free (you can leave the very end of the shell on or off, depending on what you prefer).
Once the shell is off, check to see if there is a black line running down the back of the prawn. This is the intestinal tract - if it's black, it's full. It's not harmful to eat, but the prawn looks better without it, and it can be a bit gritty. Removing it is called 'deveining'. Using a small, sharp knife, make a shallow cut along the length of the black line, then lift it out using the tip of the knife.
To butterfly a prawn, peel and devein as above, leaving the tail on. Then make a deep cut along the belly of the prawn, open it out and press it down so that it's flat. If you want the prawns to be straight, peel (leaving the very end of the tail on) and devein, then insert a wooden skewer along its length.
Like all shellfish, prawns go off quickly, so keep in the fridge wrapped in their original packaging or in a sealed container. Eat within 24 hours of purchase.
Stir fry (2-6 minutes, according to size). Grill or barbecue (3-4 minutes each side). Poach (3-10 minutes, according to size).