Grind together ginger, garlic, coriander powder, chilly powder, turmeric powder and salt.
Apply half of the ground masala onto the fish pieces. Keep aside for 30 mins.
Fry the above marinated fish, till half cooked.
Remove them from the pan.
Fry onion, curry leaves and the remaining paste, till oil separates.
Add tomato and saute nicely.
Add garam masala and fennel seeds along with coconut milk and 1/2 cup of water.
Allow it to boil.
Add half fried fish to this gravy.
Cook on low flame for about 10 mins.
In between, turn the fish, cover and cook.
Add vinegar.
Top with coconut oil.