Soak rice for 15 minutes, drain the water and keep the rice in a colander.
Meanwhile grind all the ingredients given in the list 'To Grind' with enough water as fine paste.
Heat enough oil in the pressure cooker and fry the whole spices, add the onions saute until they turn translucent, now add the ground masala, turmeric powder, garam masala powder and fry until the raw smell goes away.
Add the prawns, saute everything for few minutes.
Finally add the coconut milk and bring to boil.
Add the rice and salt and cook everything in pressure cooker with lid closed, cook in simmer for few minutes until the rice get well cooked.