Rinse and soak coccum in ¼ cup lukewarm water. Set aside.

Meanwhile, heat oil in a frying pan over medium heat. Add mustard seeds and fenugreek seeds. Let them crackle. Add one sprig of curry leaves. Fry for few seconds.

Add shallots, garlic, ginger and green chilies. Sauté, stirring occasionally, for 3-4 minutes or until browned.

Add garlic, ginger and green chilies. Sauté, stirring, for 2 minutes or until fragrant. Reduce the heat to low. Add ground turmeric, ground coriander (if using), and red chili powder. Sauté, stirring, for 1 minute or until aromatic.

Add 1 ½ cups water. Season with salt. Stir to combine. Bring to boil. Add fish pieces and soaked coccum with water. Add a sprig of curry leaves. Stir gently to combine.

Cook, covered, for about 6-7 minutes or until fish is cooked through. As the cooked fish pieces are very delicate, stir very gently.