Soak the fish tamarind in a cup of water and keep aside.
Heat oil in a deep pan, and fry the onions till translucent
Add ginger and garlic and saute until soft.
Mix the red chilli powder and turmeric powder with a few drops of water to make a paste. Add the spice paste to the pan and fry on low heat till the oil separates.
Add salt and pepper, the soaked fish tamarind pieces along with the water and one more cup of stock and bring to a boil.
Pan fry the fish fillets until just cooked (you can finish them in the oven if necessary).
For the seasoning
Heat oil in a small frying pan and add the fenugreek seeds and fry till brown. Now add the mustard seeds and when the mustard seeds start to splutter add the curry leaves and fry until brown.
Plating up
Lay the fish fillets out on the plate and spoon over the curry sauce.
Pour the seasoning over the fish and curry sauce, sprinkle with the crisp shallots and garlic, garnish with coriander sprigs.