Use a sharp knife and score deep criss-cross cuts on both sides of the fish. Marinate fish with salt and pepper, making sure to get the seasonings into the slits. Deep-fry the fish in hot oil until golden. Remove and place fish on a serving dish. Leave 3 tablespoons oil in the wok. Fry spice ingredients until fragrant. Add curry leaves and onion. Stir-fry well.
Add lime juice, chicken stock and seasoning to mix. Add chilli then dish out the sauce and pour over the fish.