Wash the rice in a sieve under cold running water until the water from the rice runs clear. Drain. Peel and devein the prawns, then wash thoroughly and pat dry with paper towels.
Heat the oil in a karhai or heavy-based frying pan over low heat and fry the onion, cinnamon, cardamom, cloves, bay leaves and lemon grass until the onion is lightly browned. Stir in the garlic, ginger and turmeric. Add the prawns and stir until they turn pinkish. Add the rice and fry over medium heat for 2 minutes. Add