Put the fish steaks on a tray and squeeze the lemon over them with a sprinkle of salt and turmeric.
Rub this over the fish and set to one side for 20 minutes.
Crush the cumin seeds. Put the coconut, green chillies, coriander and mint leaves, ginger and garlic, a little salt and the crushed cumin into a blender and grind to a smooth paste. And a dash of water if required.
Coat the pieces of fish all over and keep aside.
Pat dry the banana leaf pieces and smear lightly with a little oil on the smooth side.
Place one piece of fish in the center of each piece of leaf and wrap into a neat parcel. Tie with twine from the leaf or with a toothpick.
place in the smoker for an hour until the fish is cooked through