Use the same skillet and the fish fried oil for frying the rest of the ingredients for the fish curry.
Set the skillet over meidum heat. Add little more oil if need be. Though you won't need any more oil now because catfish will release lots of oil.
When the oil becomes moderately oil add all the whole spices like black pepper corns, cumin and coriander seeds. Saute them for just a few seconds.
Add the diced ginger and garlic and saute for a minute.
Next, add the sliced onions and saute them for 1-2 minutes. You may add salt at this stage.
Add the chopped tomatoes, dry spices & the grated coconut. Saute them for 2 minutes.
Now, add the soaked Kashmiri red chilies, the tomato paste & the puree and saute them for 1-2 minutes.
Pour about 2 cups water and give everything a very good stir. Cover and cook for 5 mins over medium low heat or until the onion is soft and the tomatoes are mushy.
Turn off the heat and allow the mixture to cool down completely. Grind it into a fine paste in a mixer grinder.
Strain the fine masala paste with the help of a strainer. This will give you a smooth and silky masala paste without any lumps or textures.