First clean the prawns and marinate it with salt and turmeric powder and keep aside for 10-15 mins
Then heat oil in a non stick pan and fry that marinated prawns for 5-10 mins and keep aside
Then in same pan add some oil and fry that patato cubes till light brown and keep aside
Then take some oil in pan and add onion paste and fry it for 4-5 mins.
Then ginger garlic paste, turmeric powder, chilli powder,Garam Masala powder and fry for 4-5 mins on medium heat.
Then add chopped tamatoes, salt into it and fry it till oil separates from masala.
Then add fried prawn, patatoes and fry it for 2-3 mins.Then add coconut milk, water and mix well.
Cover and cook on medium heat for 10-12 mins.
Garnish it with coriander leaves and serve hot.