Bring the court bouillon to the boil, plunge in the lobsters and cook for 10 minutes. When cooked, remove them from the court bouillon and allow to drain and cool slightly. Wash the leek and celery and cut into small, rough dice. Remove the leaves of herbs from their stalks, reserving the stalks. Mix the leaves and put to one side. When the lobsters have cooled, break off their tails and claws. Remove the tail meat; keep the end of the tail in one piece to use as a garnish. Crack the claws and arms and carefully remove the meat, keeping it all as whole as possible. Cut each tail into 2 lengthwise and remove the tract. Cover and keep warm.
To make the sauce, break away the underside of the head section, where the legs join the body – this should bring out the insides. Just behind the head is a groove in the shell that runs across and round underneath. Using a pair of heavy scissors, cut along this groove, wash the head well and save for garnishing. Chop up all of the legs, the coral and the intestines, discarding the gritty sac. Heat the butter in a saucepan and add the roughly cut vegetables and garlic. Fry gently, without colouring, for a couple of minutes, then add the chopped lobster. Continue frying for about another minute, again without colouring. Add the brandy, ignite and burn off the alcohol, then add the sherry and the fish stock. Bring to the boil, add the stalks from the herbs and reduce by three-quarters. When reduced, strain the stock through a strainer into another pan. Bring the stock back to the boil, add the cream, and reduce until it starts to thicken.