In a deep heavy-bottomed vessel, heat the oil and add the mustard seeds and let them splutter.
Add the chopped onion and fry until brown on a medium heat.
Add the freshly grated ginger, garlic, green chilli, mint leaves, coriander leaves and turmeric and fry for a minute.
Add the tomato and prawns and fry until the water from the prawns comes out.
Now add the rice, water and salt and cook under lid on a very low flame.
Cook until all the water is absorbed and switch off the flame.
Let this rest for a while (approximately 10 minutes) and serve hot.