Heat MudPot (if you don't have one), use a normal heavy based pan
Heat Gingelly Oil (Nallennai), Add Karuvadagam (or Mustard Seeds)
Add Curry Leaves and slit Green Chillies (2)
Add Finely Chopped Small Onions (15). You can also coarsely grind them
Once it is soft, add Chilli Powder (2-4 tsp), Coriander Powder (3 tsp), Turmeric Powder (1 tsp). If you have Fish curry powder (e.g Baba's Brand), add 2 tsp of this instead of Coriander Powder
Add little water if it gets too dry instead of oil
Add finely cut Tomatoes (3)
Cook till tomatoes are mashed up
Option to add few ladies finger or Mango
Add strained Tamarind juice (from about 1 lemon size ball)
Add salt and little sugar
Add little coconut milk or coconut powder, Fennel powder (1 tsp)
Taste and adjust spices accordingly. Gravy should not be too watery
Finally add Fish. Best Eaten the next day