Marinate prawns with 1/2 tablespoon ginger, garlic, chilly powder, turmeric powder and salt.Keep aside for 15 mints .Now cook the prawn with some water.Once its cooked strain the praws stock and keep aside.
Take a pan heat 4 tablespoon ghee , add cashews and then raisins. Roast it and keep aside. Add the onion slice and fry them till it becomes brown in color and set aside.
Heat oil in a frying pan and shallow fry the prawns and set aside. add thinly sliced onion to left over oil .Add ginger,garlic,green chilli paste and saute .When the onions start turning translucent and soft, add the tomatoes and chilli powder,1/2 tsp garam masala .
Saute until the raw smell of the masala goes. Now add the prawn ,coriander leaves and lime juice .Mix well and cook for another 10 mints
Soak the rice for 10mins and drain keep it aside. Take a heavy bottomed pan heat the ghee in the pan,add sliced onions,all spices and saute for few mins.Add the rice and fry it for 3-4 minutes .
Add the prawn stock and remaining water (total u need 4 cups) , salt and lime juice and cook it covered till it is done.Once its done off the stove and let the rice rest for 15 mints.
Layering:Transfer half the rice to a plate. Now spread the prawn masala. Sprinkle garam masala ,fried cashews, raisins, fried onions and chopped coriander leaves , sprinkle left over ghee and then transfer the rice set aside in the plate on top of the masala .
And close with a tight fitting lid and cook on low heat for 5 mints.Mix well and serve.