In center of each of four 12 x 12-inch pieces foil, place butter. Top with fish, leek, carrot, tomato, olives.
Mix wine, thyme, salt, pepper and basil in bowl; sprinkle over fish. Fold edges of foil up and together in double pleat to seal. Place on baking sheet.
Bake in 350 degree F oven 35 minutes, until fish is opaque.