1. Clean the fish pieces and marinate with 1/4 teaspoon turmeric, 1/2 teaspoon red chili powder and salt  for 10 mins2. Shallow fry the fish pieces in half of the oil on medium heat, 4 mins on each side.3. Dry roast the grated coconut on medium low heat till it turns light brown.4. Put the onions, dry roasted coconut, coriander powder, ginger, garlic, tamarind concentrate,1 green chili, remaining turmeric, red chili and salt in a blender(grinder) and grind to a smooth paste. Add water to get a smooth consistency.5. In a large sauce pan add the remaining oil, heat the oil on medium heat,then add the mustard seeds, cumin seeds, 1 dry red chili and 10 curry leaves.6. When they start to splutter add the ground mixture and simmer the gas. Cook it for 10 to 15 mins till the raw smell of onion is gone.7. Add the cubed carrots and potatoes and cook for 2 mins.8. Add 21/2 cups of water and increase the heat to medium high.9. When water starts boling simmer the gas and add shallow fried fish pieces, frozen peas, chopped spinach and remaining curry leaves. Allow it to cook for 10 mins, the gravy should turn medium thick. Take off the heat and garnish with chopped coriander leaves.10. Serve hot with steamed basmati rice.Tip: You can substitute the dry coconut powder with about 1 cup of coconut milk. In that case reduce the amount of water used.