Leiths' guide to preparing and cooking prawns

In this masterclass with Leiths School of Food and Wine, we learn how overcome the fiddly task of de-shelling prawns

Shellfish

Preparing shellfish can seem time-consuming, but the reward is in the eating. Shellfish can be divided into two main categories: crustaceans and molluscs.

Crustaceans are all the multi-jointed creatures such as crab, lobster, langoustines and prawns.

Molluscs include clams, mussels, scallops, oysters, squid and octopus. It is vital to cook and eat shellfish when they are very fresh, as they deteriorate quickly and can cause food poisoning.

Ideally they should be bought live from a reputable supplier and cooked within 24 hours. If you cannot source live shellfish, buy freshly prepared uncooked or cooked shellfish.

Crustaceans

Most of these shellfish are graded and sold according to size, and in certain countries it is illegal to buy very small ones.

However, bigger does not necessarily equate to better, so look for medium-sized shellfish where possible.

To ensure the best quality, shellfish should be bought live from a reputable fishmonger (Peter Cassidy)

All live shellfish bought from a fishmonger in this country will have a health certification so it is best to buy from one if you can.

If gathering your own, be aware that shellfish gathered from polluted waters can present a health risk; gather from the sea rather than from estuaries or harbours.

Prawns

Prawns can be purchased raw or cooked, with heads on or off. It is most economical to buy tails only, as more meat is obtained by weight. However, a whole prawn has more flavour, as do the heads and shells of any shellfish.

Even if you are buying them pre-cooked, they will be full of flavour and can be used to produce excellent stocks and sauces.

Prawns are generally graded by size for sale and are sold by weight, so the bigger they are the more expensive they will be. As an approximate guide, 20-25 prawns per kg yields prawns of a suitable size for most recipes.

Unless local and fresh, prawns are either cooked as soon as they are caught or are deep frozen because, as in the case of crab and lobster, the meat loses flavour and texture very quickly.

So even when a sign in a fishmonger says “fresh prawns”, unless locally caught, they may be frozen and defrosted. Where possible buy prawns still frozen, rather than defrosted, as they deteriorate quickly after defrosting. When checking for freshness, look for tails that are still firm and taut. There should be no obvious discoloration.

Preparing and peeling raw shell-on prawns

1. Hold the prawn by the tail. Using your other hand, twist the head and pull it away from the tail. Put the heads aside (they are full of flavour and, along with the tail shells, can be frozen and used later to make shellfish stock) (Peter Cassidy)

2. Peel the tails. The tail shells are soft and hinged and can be removed piece by piece or in several pieces at a time. Start to peel away the shells from the underbelly of the prawn. The tail tip can be kept on or carefully removed (Peter Cassidy)

3. Make a shallow incision, 1-2mm deep, down the length of the back of the tail to expose the intestinal tract (this is usually dark, but it can be almost translucent). Carefully pull this away and discard. The prawn tails are now ready to cook (Peter Cassidy)

Butterflying raw prawns

Shell-off

1. Holding the shelled prawn between your fingers and thumb, make a shallow incision, along the length of the back of the tail to expose the intestinal tract. Carefully pull this thread away and discard (Peter Cassidy)

2. Cut down between the natural 2 halves of the prawn, halfway down, to butterfly the prawn, leaving the tail tip intact (Peter Cassidy)

Shell-on tip: After pulling away the head, turn the prawn over so it is belly-side-up and cut halfway through the prawn, keeping the tail tip intact.

Leaving raw prawns whole and shell-on for cooking

1. The intestinal tract will still need to be removed. To do this, bend the prawn a little at the point where the head meets the tail. Using a small knife or cocktail stick, isolate and break the intestinal tract. If you are not serving the prawn with the head on, then twist it off, leaving the head end of the tract unattached (Peter Cassidy)

2. Bend the prawn before the last tail section, to separate the tail sections. Using the point of a small knife or cocktail stick, hook the intestinal tract from underneath and gently tug at it. As it has been released at the head end it should be possible to pull it through the length of the tail and out quite easily. Do not pull too firmly or it will break (Peter Cassidy)

3. On larger prawns, you can tug and twist at the little triangular shell on top of the tail, which the intestinal tract is attached to, and gently pull out the tract (Peter Cassidy)