Prepare the grill for direct cooking over high heat (230° to 290°C).
Prepare the grill for cooking over high heat (260°C).
Pat the halibut dry with paper towels. In a medium bowl combine 2 tablespoons of the peanut oil, 1 tablespoon of the dark green scallions, 1 tablespoon of the cilantro, ¾ teaspoon salt, and ½ teaspoon pepper. Add the halibut and turn to coat.
Set a large plate and all the ingredients close to the grill.
Brush the cooking grates clean. Grill the halibut over direct high heat, with the lid closed, just until grill marks appear and the outside of the fish feels firm but the fish is still raw in the center, 2 to 3 minutes, turning once (the fish will continue to cook in the soup). Transfer the fish to the plate.
Brush the cooking grates clean. Grill the halibut over high heat, with the lid closed, just until grill marks appear and the outside of the fish feels firm but the fish is still raw in the center, 2 to 3 minutes, turning once (the fish will continue to cook in the soup). Transfer the fish to the plate.
Place a large, deep grill-proof pot directly on the cooking grates over direct high heat. Add the remaining 2 tablespoons peanut oil to the pot and heat for 1 to 2 minutes. Add the white and light green scallions, ¼ cup of the remaining cilantro, the ginger, and garlic. Cook until fragrant, 1 to 2 minutes, stirring occasionally. Add the curry paste and cook for 30 seconds, stirring constantly. Add the coconut milk and clam juice and bring to a simmer, stirring often. Stir in the fish sauce and lime zest and juice. Stir in the carrots and bell pepper and bring to a simmer. Cook until the vegetables are crisp-tender, 3 to 5 minutes. Add the bok choy and simmer until the bok choy and all the vegetables are tender, 4 to 5 minutes more. Add the fish and simmer gently until the fish is just opaque in the center but still moist, 1 to 2 minutes. Stir in the basil, the remaining 3 tablespoons cilantro, and the remaining dark green scallions. Season with ½ teaspoon salt and ½ teaspoon pepper. Keep the grill lid closed as much as possible during cooking.
Place a large, deep grill-proof pot directly on the cooking grates over high heat. Add the remaining 2 tablespoons peanut oil to the pot and heat for 1 to 2 minutes. Add the white and light green scallions, ¼ cup of the remaining cilantro, the ginger, and garlic. Cook until fragrant, 1 to 2 minutes, stirring occasionally. Add the curry paste and cook for 30 seconds, stirring constantly. Add the coconut milk and clam juice and bring to a simmer, stirring often. Stir in the fish sauce and lime zest and juice. Stir in the carrots and bell pepper and bring to a simmer. Cook until the vegetables are crisp-tender, 3 to 5 minutes. Add the bok choy and simmer until the bok choy and all the vegetables are tender, 4 to 5 minutes more. Add the fish and simmer gently until the fish is just opaque in the center but still moist, 1 to 2 minutes. Stir in the basil, the remaining 3 tablespoons cilantro, and the remaining dark green scallions. Season with ½ teaspoon salt and ½ teaspoon pepper. Keep the grill lid closed as much as possible during cooking.
Ladle the soup into four large bowls and serve immediately with freshly squeezed lime.
Note: The soup would also be great with scallops and shrimp instead of the halibut; salmon, cod, or mahimahi would also work well. For a more substantial meal, ladle the soup over bowls of hot cooked rice.
