Peel and finely chop the garlic. Wash the basil and dab dry. Peel the leaves and chop finely. Wash lemon hot, grate dry, grate peel finely. Mix garlic, basil and lemon peel.
Wash the fish, rub dry and cut diagonally on both sides of the bones. Place basil-lemon gremolata and salt in the spaces between the bones. Season fish with salt from the outside, place on a hot grill and grill briefly on both sides.
Remove from the grill and wrap in 1 banana leaf each. Close the ends with wooden skewers. Grill the fish indirectly at medium heat for about 25 minutes. Wash the chives, dab dry and cut into small rolls, except for a little garnish.
Drain the olives in a sieve. Wash and clean the tomatoes and cut them into pieces. Season the vinegar with salt, pepper and sugar and add oil drop by drop. Mix tomatoes, olives, chives and vinaigrette.
Season again with salt and pepper. Garnish with chives. Cut lemon into slices and serve with fish.