Soak cocum (kudampuli) in 4 tablespoon salted luke warm water for 15 - 20 minutes.
Heat oil in a pan. Saute small onion , ginger , green chilly and curry leaves.
Once onion turned light brown, add turmeric, chilly and coriander powder. Keep it in low flame. Saute it well.
Add thick and medium coconut milk. Add water in which cocum was soaked. Taste the mixture and add soaked cocum pieces as required. Add enough salt. Keep it in low flame.
Bring it to boil and then add cleaned fish pieces. Cook it till fish gets cooked and gravy is consistent. It would take around 20 minutes.
Garnish with fried small onions and curry leaves.
Notes
Try making this curry in a clay pot (manchatti) for better flavor. Always clean and season the pot before use.
Avoid using high flames. Spices can burn and turn bitter, coconut milk may split, and fish can break if cooked too fast.
If using frozen fish, always thaw it fully before cooking. Wash it last with a little salt to remove any smell, scales, or dirt. Once added to the curry, avoid stirring too much. Both overhand ling and poor thawing can cause the fish to break.