Dry roast the fennel seeds, black peppercorns and coriander seeds, then grind in coffee grinder.
Heat the oil in a sauce pan and add the onions, sauté to soften. Now toss in the ginger and garlic and lightly sauté to cook through. Add the dry roast spices, the tamarind and the chilli powder. Pour in the fish stock and chopped tomato.
Bring to the boil and then reduce to a simmer and cook until the liquid has reduced by half.
Strain, pressing against the solids to remove as much flavour as possible - Discard the solids.
Bring the reduced liquid to the boil, toss in the mussels, cover with a lid and cook for 3-4 minutes until mussels have opened.
Meanwhile, heat the vegetable oil to smoking hot, add the asafoetida, crackle the mustard seeds then add the curry leaves and chilli.
Once the spices are all tempered, pour onto the mussels, stir through and sprinkle with chopped chives.
Served with a crusty bread such as the Onion and Cumin Bread.