Cut Fish into 2 inch squares, anything smaller will fall apart. Then set aside.
Soak Kokum Star in 1 cup or more of water. Enough water to emerge the Kokum Star. This is a key ingredient as it adds the tangy flavor to the dish. I have used Tamarind as a substitute. If you do then make sure to remove the black seed. Let this soak in the water for at least 10 minutes. The longer the better.
In a deep pan heat the oil. Add the mustard seed and cover for 2 minutes (Mustard Seeds will splutter so do not leave it uncovered).
Add in the Onion, Garlic Paste, Ginger Paste and 2 sprigs of Fresh Curry Leaves (remove off the stem). And saute for 2 minutes. By now your house should smell like an Indian Restaurant.
In a small bowl mix Chili powder, Turmeric powder, Fenugreek powder and salt with 4 tablespoons of water into a paste. Then add paste into the pan and stir. Saute for 3 minutes.
Add Kokum Star with water, stir and bring the heat on high. Then add in the fish pieces while keeping the flame high until the water boils for 5 minutes.
Reduce the flame and gently stir without breaking or damaging the fish pieces. Add the remaining 2 sprigs of fresh curry leaves and cook on low heat for 20 to 25 minutes.
Lastly, remove off heat and add in the coconut milk slowly and mix in without damaging the fish pieces. Let it sit for 10 minutes or longer. Then serve with Rice or Indian bread. Usually the flavors will intensify the next day and it will taste even better!