DEBOLINA ROY
Prepare the marination: The fresh, firm fish fillets should be cut into uniform bite-sized portions. Using plenty of turmeric powder and salt, marinate the fish thoroughly for 30 minutes to allow the fish to soak in all of the seasoning.
Paste the spice: In a small bowl, combine the Kashmiri chilli powder, turmeric, salt, asafoetida, and roasted fenugreek powder with hot water. It creates a smooth, creamy spice paste that is essential for Kerala style fish pickle.
Frying: In a saucepan, heat aromatic gingelly oil. Fry the marinated fish till golden crisp. Next, fry the sliced garlic, chopped ginger, fresh green chillies, and bright green curry leaves one at a time and then drain.
Prepare the gravy base: Fry mustard seeds in the leftover hot oil, add sautéed ginger-garlic, and mix in the spice mixture. Pour in the mild vinegar and bring to a boil; turn down the heat immediately.
Coating: Add the filets and fried spices into the boiling sauce. Combine all equally so they're well coated, and simmer for 1 minute. Let it cool completely before transferring to jars for storage.