Heat 2 tbsp of the butter in a medium saucepan and gently cook onion, fennel, garlic and salt, until softened.
Add lemon zest and 250ml of the white wine. Bring to the boil and allow to reduce slightly. Add the fish stock and bay leaf, bring back to the boil, then reduce heat and simmer for a further 5-10 minutes.
Add the infused saffron and double cream to the broth and reheat gently without boiling.
Meanwhile, place the mussels, squid and sugar snap peas in a large stockpot together with the remaining 50ml of wine, lemon juice, half the thyme and 1 tablespoon olive oil. Cover tightly with a lid and cook over high heat for 4 minutes or until mussels open. Remove from the heat.
Heat remaining olive oil in a frying pan. Lightly season scallops and cook on each side until golden. Remove from pan and set aside. Lightly season king prawns and fry for two minutes on each side. Add the fish to the pan and cook for a further 3 minutes.
Return the scallops to the pan with remaining butter and the rest of the thyme. Cook for a further 30 seconds and remove from the heat.
Divide the seafood evenly between 6 serving bowls.
Add the liquid from the mussel pot to the saffron broth and adjust seasoning to taste. Ladle the broth and vegetables over the seafood in the bowls.
Garnish with fresh herbs and serve with crusty bread or your favorite pasta.