Wash the fish and pat dry. Place in a non-metallic bowl, then marinate in the lime juice and salt for 30 minutes.
Preheat oven to 125 °C
to assemble the parcels
Heat a small frypan over medium heat. Add the coriander and cumin seeds and toss gently until the seeds start to colour and become aromatic. Remove from the heat, allow to cool then grind to a fine powder.
Place the ground seeds and the remaining chutney ingredients into a mortar and pestle or blender with as little water as possible - start with a few tablespoons - and make a smooth paste. Set aside.
Wash and dry the banana leaves then place them in the oven for five minutes.
Bring a pot of water to the boil, and place the steamer basket over.
Cut banana leaves into suitable sizes for fish parcels. Place one teaspoon of the coconut and coriander chutney on each of the parcels, then place a piece of the fish on the chutney. Spread one more teaspoon of the chutney on top of the fish, then wrap the parcel and tie it using kitchen twine. Reserve the remaining chutney.
to cook
Arrange parcels in one layer in the steamer. Steam for 25 minutes.
to serve
Remove parcels from steamer, and serve with wedges of lemon and the reserved chutney.
notes
Any firm white fish will be suitable. Cod is a good choice.
The step of warming the banana leaf before preparing the parcel is important. This makes the leaf pliable and less likely to split when folding and tying.
If banana leaves are not available the parcels can be made from grease-proof or baking paper.