Add some water to the green tamarind pods and boil till soft.
After cooling extract pulp.
Clean each fish carefully. Add gingergarlic paste, red chilly powder, one spoon salt, two spoons oil and mix well. Allow to marinate.
Add all the ingredients of spicy paste to a grinding jar and prepare a paste.
To a deep bottomed pan add oil and heat. Splutter mustard seeds and add the onion pieces. After the onion pieces turn brown, add the spicy paste and fry till the raw smell is gone. Add the curry leaves, marinated fish and sufficient salt. Mix well and fry carefully till oil shows up.
Add the green tamarind pulp, mix thoroughly, add three cups of water and some salt if necessary. Allow to simmer on medium flame till the cooking is done.