Rub the fish steaks with salt, vinegar/lime juice and keep aside.
Dry roast the grated coconut, till golden brown and keep aside.
Dry roast the coriander seeds, cumin seeds, fennel seeds and fenugreek seeds, till they turn a shade darker and aroma fills the air. Keep aside.
In a pan, heat 2 tsps of oil and when hot, add the chopped onions, ginger and garlic. Saute, till the onion turns brown in colour.
Add the chilli powder and stir for a minute. Switch off the heat and let it cool.
Grind the roasted coconut, along with the coriander seeds, cumin seeds, fennel seeds, fenugreek seeds and the onion mixture, vinegar, cinnamon, star anise, cloves and salt, to a fine paste. Adjust the seasoning.
Wilt the banana leaves, by holding over low flame. The wilted leaf can be folded easily, without breaking.
Take a leaf and spoon in a bit of the ground masala. Place a fish piece on top of the masala and put a spoonful of masala on top of the fish. Cover the fish with the leaf and make parcels.
Steam the fish parcels for 20 minutes or till done. Serve hot.