Bring a large saucepan of lightly salted water to the boil and cook the pasta according to the packet instructions or for about 10 minutes, until tender. Drain well.
Fry the chopped onion and garlic for 5 minutes in a pan over medium heat with the olive oil.
Preheat the oven to 190 C / Gas 5.
Place the chopped tomatoes, courgettes, mushrooms, onion and garlic mixture and basil in a large saucepan and heat gently for a few minutes.
Mix the cooked pasta into the tomato sauce mixture. Add the prawns and season with salt and pepper, and mix well. Spoon it all into an ovenproof dish and drizzle over the yoghurt. Sprinkle the Parmesan cheese on the surface.