Prawns are most commonly bought ready prepared. For those that feel like getting a little mucky, Gordon demonstrates in this Cookalong video how simple it is to peel and de-vein prawns.
When cooking with any fish, you want to buy it as fresh as possible. The best way of knowing that your fish is fresh is by smell, or lack of smell. The less it smells of fish, the fresher it is.
If buying shell-on prawns, you want to buy double the weight as ready shelled prawns.
Take the body of the prawn and, with the other hand, twist off the head.
One of the advantages of buying prawns with their shell on is that the heads have great flavour and can be used for stocks or sauces.
Turn the prawn over and, with your fingers, pull the shell open along the belly. Start at the top working down towards the tail. As you work your way down the prawn push it away from the body so that eventually the prawn will become free from the shell.
Once the prawn is free of its shell, turn it over to see if there is a black line running down the back. If there is this is called the intestinal tract. Although it's not harmful to eat, the prawn will benefit from having it removed.
Using a small, sharp knife, make a shallow cut along the length of the black line. Now lift it out using the tip of the knife.
Repeat this process with the remaining prawns, and they are ready to cook with.