Wash fish again throughly and leave in refrigerator for another hour.
Chop and make fine paste of Ginger and Garlic. (You may used ready chopped ginger and garlic paste if preferred.)
Heat up oil or clarified butter in a deep pan and put the ginger and garlic paste in it.
Stir for two minutes, then put ½ cup water and let it get brown by constantly stirring.
Add red chilli powder, salt, cumin, and turmeric powder. And stir until all water dries.
When water dries up, add the curd a little at a time, and fry it. Keep adding plain yogurt until it dries up and makes a thick curry.
Add fish pieces now, and fry lightly by stirring.
Add water to the requirement. Let the fish get the curry flavor, then serve.