1 Pour 3 pints boiling water into a 2.25 litre/4 pint (10 cup) heatproof mixing bowl. Add salt and oil.
2 Hold the spaghetti in boiling water curling round as the pasta softens, so that all is eventually immersed.
3 Cover with plastic wrap (lift one corner), or a lid, and microwave on full power for 8 minutes. Set aside, covered.
4 In a large jug put tomatoes, tomato puree (paste), prawns (shrimp), crab meat and olives. Add salt and pepper to taste.
5 Cover with plastic wrap, and pierce. Microwave on full power for 6 minutes, stirring once, half way through cooking.
6 Cream the cornflour (cornstarch) to a smooth paste with a little cold water and stir into the hot seafood sauce. Return to the microwave on full power for 1 minute. Stir.
7 Drain the spaghetti, arrange it on a serving dish and pour over the seafood sauce.
8 Sprinkle liberally with Parmesan cheese, and garnish with olives. Serve with a mixed salad.