Heat 2 tbsps of coconut oil in a pan on medium heat and throw in the mustard seeds.
As they crackle, reduce the heat and add the curry leaves followed by the shallots. Saute for a minute or two till translucent but not brown.
Now put in the ginger, garlic, green chillies and turmeric powder and cook for 20 secs more.
Gently tip in the fish and stir to coat with the other ingredients. Mix lightly so as to avoid breaking the delicate fish.
Cook for 5-7 minutes and add the salt and grated coconut. The fish will be done at this point.
Saute for a minute more, drizzle the remaining tbsp of coconut oil on top and take the pan off the heat. Serve hot or at room temperature.