Place wine in a wide pan over medium-high heat. Bring to a simmer, then add mussels and cover. Cook, shaking the pan occasionally, for 3 minutes until almost all shells have opened (discard any mussels that remain unopen after this time). Strain, reserving liquid, then remove mussels from shells and set aside. Place reserved liquid, fish stock and saffron in a pan and keep at a simmer over low heat.
- Melt 30g butter with 1 tablespoon oil in a large, heavy-based frypan over medium heat. Add prawns and cook for 2-3 minutes, turning, until cooked through. Remove to a bowl and set aside. Increase heat to high. Add squid and scallops. Cook, turning, for 1-2 minutes until just opaque and almost cooked through. Set aside with prawns.
- Reduce heat to medium and melt remaining 10g butter with remaining 1 tablespoon oil. Cook the onion, stirring, for 2-3 minutes until softened. Add garlic and rice and stir for 1-2 minutes to coat the grains. Add a ladleful of hot stock and stir until absorbed. Continue adding stock, 1 ladleful at a time, stirring and making sure each is absorbed before adding the next, until rice is al dente. This will take about 20 minutes. (You may not need all the stock.) Stir in the seafood, passata or sugo and parsley. Season and cook for 1 minute until heated through. Serve garnished with parsley.