Ingredients
2 live lobsters, each about 500g/1lb 2oz
at least 16 good-sized live langoustines in shell
salt
4 large handfuls of fresh mussels in shell, about 800g/1lb 12oz total weight
4 smaller handfuls of fresh clams in shell
a few fresh razor clams in shell
50g/2oz unsalted butter
1 small onion, finely chopped
glass of white wine
squeeze of lemon juice
large handful chopped parsley
salt and freshly ground black pepper

Method
1. Fill a large stockpot with water and bring to a furious boil. Season with plenty of salt. Drop in the lobsters, put the lid on the pan and bring back to the boil as quickly as possible. After 12 minutes, remove the lobsters from the pan with tongs and transfer to a tray. Cool. Return the water to the boil, drop in the langoustines and cook for 45 seconds. Remove these and transfer to a tray too.
2. Scrub the mussels well and then remove the beards from the mussels and discard them. Wash the mussels well under cold, running water. Wash the clams in a similar fashion. Discard any mussels or clams that don't close when gently tapped.
3. Melt the butter in a large pan, add the onion and cook gently until softened, but not coloured. Turn up the heat. Tip in the mussels, add the white wine and season with salt and freshly ground black pepper. Place the lid on the pan, shake gently and let the mussels steam open. Discard any that remain firmly shut. Once opened, remove the mussels with a slotted spoon to a bowl and cover with a damp cloth.
4. Place the clams in the liquid in the pot and steam open in the same way, remembering to discard any that do not open, then transfer to a bowl and cover. Do the same with the razor clams.
5. Pour the cooking liquid from the mussels and clams into a medium pan, checking closely for any grit and straining if required. Add 150ml/¼ pint of water and bring to the boil, then set aside. This is the broth.
6. Pull the claws from the lobsters and crack well to remove the meat. Split the tail lengthways and remove the meat from the shell. Remove the langoustines from their shells. Slice the lobster and langoustine meat. Take all the clams and mussels from their shells.
7. To serve, bring the broth to the boil and add a squeeze of lemon juice and the parsley. Add salt and freshly ground black pepper to taste, then stir in all the shelled shellfish. Ladle into bowls.