First prepare the octopus legs. In a large pan with a tight-fitting lid, sauté the onion and garlic to colour in a little vegetable oil. Add the octopus and give it a stir, then add the lemon, 1 litre of water, 2 teaspoons flaky salt and the peppercorns. Sit a cartouche on top of the liquid and bring to the boil. Turn to a simmer, put the lid on, and cook for 80 minutes. Turn the heat off and leave it to cool in the liquid. Once it’s cool, remove the octopus from the liquid, strain the liquid, pour it back over the octopus and place in the fridge.
Preheat the oven to 160°C. Line a roasting dish with baking parchment. Cut the pumpkin into 12 even-sized chunks - there’s no need to peel it unless you want to. Pound the cumin, allspice, sesame seeds and chilli flakes with 1 teaspoon flaky salt and sprinkle this over the pumpkin, drizzle on the olive oil and 50 ml water. Roast until you can insert a thin sharp knife through the flesh of the pumpkin.
Heat up a wide, deep pot and when it begins to smoke tip in the clams, all at once, and put a lid on. Cook for 4 minutes, shaking the pan from time to time. Turn the heat off and discard any clams that haven’t opened. Tip the clams into a colander and leave to drain, then strain the pan juices through a fine sieve and reserve for later use - it makes a great addition to a fish and shellfish soup and is lovely mixed into a tomato-based sauce for pasta, or mixed into a seafood risotto.
Rinse the pot out then sauté the shallots, ginger and chillies in 1 Tablespoon of the vegetable oil until beginning to caramelise. Add the baby octopus and give it a good stir, then add the saffron and its soaking liquid and coconut milk and bring to the boil. Put a lid on and cook over a high heat for two minutes. Add 200 ml of the octopus cooking liquid and bring back to the boil, then add the clams, octopus, scallops and monkfish and give it a very gentle stir. Simmer for no more than 2 minutes with the lid on then turn the heat off, taste for seasoning, and leave for a few minutes.