Ingredients
3 tablespoons extra-virgin olive oil, divided, plus more for serving
2 tablespoons tomato paste
1 pound large shrimp, peeled and deveined, shells reserved
1/2 teaspoon crushed saffron threads
2 celery stalks, cut into a 1/4-inch dice (3/4 cup), plus a handful of tender inner leaves, chopped, for serving
2 shallots, chopped (1 cup)
4 cloves garlic, thinly sliced (2 tablespoons)
Kosher salt and freshly ground pepper
2 plum tomatoes, cored and cut into a 1/2-inch dice (1 cup)
2 teaspoons fresh thyme leaves
2/3 cup dry white wine, such as Sauvignon Blanc
2 1/2 pounds littleneck clams (about 24), purged and drained
2 pounds mussels (about 48), purged and drained
1 can (14.5 ounces) seafood or fish stock, such as Bar Harbor
2 teaspoons grated orange zest, plus 3 tablespoons fresh juice
1 1/2 pounds firm, skinless white-fish fillet, such as halibut, cut into 1-inch pieces
Chopped fresh parsley leaves, for serving
Toasted Garlic-Butter-and-Herb Bread, for serving (optional)
Preparation
In a saucepan, heat 1 tablespoon oil over medium-high. When it shimmers, add tomato paste and shrimp shells. Cook, stirring, until shells turn pink and opaque, about 2 minutes. Add 2 cups water and gently boil 5 minutes. Strain shrimp broth into a heatproof bowl; discard solids. Stir saffron into broth.
Heat remaining 2 tablespoons oil in a braiser pan or wide, shallow pot over medium. Add celery, shallots, and garlic; season with salt and pepper. Cook, stirring occasionally, until fragrant, 1 to 2 minutes. Stir in tomatoes and thyme. Cover and cook until tomatoes collapse and release their juices, 6 to 8 minutes. Add wine and boil until mostly evaporated.
Add clams to pan, increase heat to medium-high, and cook, covered, just until they begin to open, 6 to 8 minutes (discard any that don’t open). Transfer clams to a large heatproof bowl and cover with a plate to keep warm. Add mussels to pan and cook, covered, just until they begin to open, about 5 minutes (discard any that don’t open). Transfer mussels to bowl with clams.
Add seafood stock, shrimp broth, and orange zest and juice to pan. Bring to a simmer over medium-high heat; simmer 5 minutes. Meanwhile, remove about half of clams and two-thirds of mussels from their shells, reserving meat and juices and discarding empty shells.
Stir shrimp and fish into pan, reduce heat to medium-low, and cook, covered, just until shrimp and fish are firm and cooked through, 3 to 5 minutes. Return shelled and in-shell clams and mussels and any accumulated juices to pan, stirring to combine. Remove from heat, sprinkle with celery leaves and parsley, drizzle with more oil, and serve with bread, if desired.
