How to Make It
Heat oven to 400° F. Combine the broth and clam juice in a microwave-safe bowl and heat until very hot, 4 to 5 minutes.
Combine the rice, 1 tablespoon of the oil, the garlic, 1 teaspoon salt, ¼ teaspoon black pepper, and the hot broth mixture in a 4-quart baking dish and stir. Cover tightly with foil. Bake for about 30 minutes, until the rice is almost cooked through and slightly soupy. Stir in the tomatoes, shrimp, and halibut and arrange the mussels on top. Bake, uncovered, for about 15 minutes longer, until the rice is tender and the seafood is cooked through. (Discard any mussels that do not open.)
Mix the chopped tarragon with the remaining 2 tablespoons of oil in a small bowl. Drizzle the tarragon oil on top of the risotto. Garnish with the red pepper and tarragon leaves.