Heat the coconut milk with the curry paste, fish and oyster sauce, sugar and lime juice in a small saucepan. Simmer gently for about 10 minutes. Stir in the cornstarch, add the basil leaves and set aside.
Prepare and mix the vegetables as indicated above.
Cut the fish fillet into 8 pieces.
Prepare eight banana leaves about 20x30cm in size.
Place 2 tablespoons of vegetables in the middle of each banana leaf (shiny side down), drizzle with 1 tablespoon of coconut milk mixture, put a fish fillet on top and sprinkle with 1-2 tablespoons of coconut milk mixture again. Carefully fold the banana leaf from the top and bottom to the middle, then carefully fold the side edges down to the middle and secure with a toothpick. Do not prick the fish.
Do this until you have eight packages.
Prepare the grill for medium indirect heat (175-220 ° C).
Grill the fish parcels for 18-20 minutes and serve immediately.
The parcels can be prepared well. Then cover with a damp cloth and put in a cool place. Allow to reach room temperature half an hour before grilling.