Grind together fresh grated coconut,pinch of fenugreek seeds, shallots,dry red chillies, turmeric powder and red chilli powder with enough water into fine paste.
Heat oil in Meenchatti / earthern wok,add sliced onions,green chillies and crushed ginger. Saute till onions turn soft and translucent.
Add the ground coconut paste and salt and cover and cook for 5 to 7 mins.
Add drumsticks and chopped tomatoes and cook for another 5 mins.
Soak a lemon size tamarind in warm water and add this to the gravy. Add enough water to adjust the consistency.
Cover and cook. When it starts boiling add in the fish pieces
Cook on high flame for 5 to 7 mins and simmer on medium to low flame for 15 to 20 mins.
Switch off the flame and for tempering heat oil in a pan,add mustard seeds,let it splutter. Add finely chopped shallots and curry leaves and saute till the onions turn brown.
Pour this on the fish gravy. Keep it covered for sometime before serving.