With a pair of kitchen snips or shears cut the shell lengthwise along the middle of the back. Repeat the process on the underside of the shell. The shell will then come apart easily in two halves. After shelling the tail fold it over in its natural curl, and cut along the middle of the back so that the two ends of the tail are intact but the centre has been cut through. Gently pull the two sides away from each other, folding the ends of the tail towards the centre. This action will butterfly the tail. It should be raw in the centre and lightly cooked on the outside. Remove the digestive vein from the tail and rinse it under cold water. If you are using a large lobster the tail may be shelled and cut into 3-cm medallions or it may be severed, with the shell intact, at the joints in the tail.