Dredge fish pieces in a mixture of salt and turmeric on a plate.
Fry fish in 15ml to 30ml of oil for 3 minutes until golden and drain on paper.
Heat remaining oil and fry mustard seeds in a covered pan until they pop.
Add grated onion and curry leaves to the pan and fry for 5 minutes.
Stir in tomatoes, ginger, garlic, chilli, and garam masala and fry for 4 minutes.
Mix in coconut cream and simmer until the sauce thickens, adding water if needed.
Incorporate the fried fish into the sauce and cook until heated through.
Serve the curry over rice and garnish with coriander.