Heat the oil in a saucepan and fry the onion and garlic for  6-7 minutes until softened. Meanwhile, cook the spaghetti on a large pan of boiling salted water for 10-12 minutes or according to the instructions on the packet, until al dente.

Stir the passata, tomato puree, oregano, bay leaf and sugar into the onions and season to taste with salt and pepper. Bring to the boil, then simmer for 2-3 minutes.

Add the shellfish, lemon juice and 30ml/2 tbsp of the parsley. Stir well, then cover and cook for 6-7 minutes more.

Drain the spaghetti and add the butter to the pan. Return the drained spaghetti to the pan and toss in the butter. Season well.

Divide the spaghetti among four warmed plates and top with the seafood sauce. Sprinkle with the remaining parsley, garnish with whole prawns and serve immediately.