Heat a kadai and add oil.
After oil gets heated, add chopped onion and sauté till it turns pinkish.
Add the marinated prawns, grated coconut, green chilies, raw mango pieces, turmeric and chili powder.
Mix everything, add 2 tablespoon water and cook with lid covered till the prawns and raw mango gets cooked.
Add salt to taste and mix.
Garnish with chopped coriander leaves.