1. Preheat the oven to 220°C (200° fan).
2. Put 300 ml of the wine in a large saucepan with the sea salt, peppercorns, onions, carrot and lemon juice. Add 1L water and bring to the boil, then reduce the heat and simmer for 10 minutes. Remove the carrot, onion and peppercorns with a slotted spoon.
3. Add the baby octopus to the saucepan and simmer for 40 minutes, adding more boiling water if they stop being submerged at any point.
4. Meanwhile, mix the flour with the cayenne and a big pinch of salt. Flour the sprats all over, as well as the skin side of the cod, patting off any excess.
5. When the octopus has been cooking for 30 minutes, heat 3 tbsp olive oil in a large ovenproof frying pan and add the cod, skin side down. Fry for 2 minutes, then turn over the sprats and transfer the frying pan to the preheated oven. Roast for 8 minutes or until cooked through.
6. While the fish is in the oven, heat the rest of the oil in a sauté pan and fry the garlic and parsley for 1 minute. Add the clams and the rest of the wine, then put on the lid and steam for 5 minutes, or until all the clams have opened.
7. When the octopus has been cooking for 40 minutes, add the king prawns and simmer for 3 minutes or until they turn opaque.
8. Add the squid rings to the octopus pan and simmer for 1 minute, then drain the whole pan through a colander and discard the bouquet garni.
9. Arrange all of the seafood in a large paella pan or on a platter and garnish with parsley and lemon