Soak tamarind in 1/2 cup of water for 10 minutes and get a thick juice. Add tomato, green chili, coriander powder, black pepper powder, cumin powder, fennel powder, chili powder, coconut paste, salt, shrimp, fried dry fish and mix well.
Fry the hyacinth bean seeds (mochai kottai) in 2 teaspoon (tsp.) oil. Add 2 cup of water and cook them.
Once the mochai is 3/4 cooked, add hyacinth bean (Avarakkai) , potato and cook them for a minute.
Now add the cut brinjal, tamarind water and cook until the raw smell is gone. Boil and cook until the right thickness is achieved.
In a separate pan heat 2 teaspoon (tsp.) of oil. add mustard seed once the mustard seed stop splattering add chopped onion, curry leaves and cook until the onion turn golden brown.
Now add tempered (onion, mustard seed, curry leaf) to the boiling mochai kottai kuzhambu. Wait for one more boil then remove from stove and serve.