Clean and wash fish, coat with turmeric and salt and set aside for 15 minutes.
Dry roast coriander seeds, cumin seeds, and peppercorns until fragrant. Transfer to a grinder. Add coconut and chilies and grind until smooth.
Heat oil in a pan. Fry fish, drain and set aside.
To the same oil add chopped onions and ginger and cook until translucent.
Add coconut and spice paste, tamarind water and cook for 5-8 more minutes, or until oil separates. Add more water if necessary
Now add the chopped candied mangoes/aamsotto and cook for 3-5 more minutes.
Adjust salt, add chopped cilantro and drizzle some more mustard oil if desired.
Serve with steamed rice.