Clean the prawns. Apply ginger-garlic paste, turmeric powder, little salt and two small spoons of oil. Mix well and leave aside for marination.
Peel the mangoes and cut into small pieces. Cut the brinjals into pieces and leave the pieces in water.
Put a deep bottomed pan on the stove. Add oil and heat. Splutter the mustard seeds, add onion pieces and after they turn brown add tomato pieces and allow to simmer.
Now add the marinated prawns and fry until oil separates. Add red chilly powder, mango pieces, brinjal pieces, some water and enough salt.
Mix well and cook until it is done. Add garam masala powder and cook for two minutes more.