Heat the oven to 400°F.

• Cut the ciabatta in half horizontally, then cut the halves in half on the diagonal. Drizzle or brush the cut sides with 1 to 2 teaspoons oil and season with salt.

On a sheet pan, place the ciabatta, cut sides up, and toast in the oven, turning once, until lightly browned and crisp, 10 to 12 minutes. Meanwhile, start the bourride.

• Trim the root end from the leek; cut the leek in half lengthwise, then crosswise into ¼-inch-thick half-moons, enough to measure 1 cup [2 cups]. Rinse and drain well.
• Cut the fennel lengthwise into quarters and cut away the core; cut the quarters into ¼-inch pieces.
• If using, set aside half the piment d’Espelette for serving.
• Strip the parsley leaves from the stems. Tie the stems into a bundle with 1 parsley stem or with kitchen twine. Coarsely chop the leaves for garnish.

In a large sauce pot over medium-high heat, warm 1 to 2 tablespoons oil until hot but not smoking. Add the leek, fennel, turmeric spice blend, and up to half the piment d’Espelette and season with salt and pepper. Cook, stirring occasionally, until the vegetables start to soften, 3 to 4 minutes.

If using, stir in ½ cup [1 cup] white wine (from your pantry) and cook until thickened slightly, about 1 minute. Add the parsley stem bundle, vegetable broth, and 1½ cups [3 cups] water and bring to a boil, then reduce to a simmer. Cover and cook, stirring occasionally, until the vegetables are very tender, 6 to 8 minutes. Meanwhile, prepare the seafood.

For shrimp:

• Rinse and drain the shrimp. Pat dry on a paper-towel-lined plate. Season lightly with salt.

For fish:

• Pat the fish dry with a paper towel. Cut the fish into 1-inch pieces; season lightly with salt.

When the vegetables are very tender, add the seafood and cook until firm and cooked through, 2 to 3 minutes for shrimp and 3 to 5 minutes for fish. Using a slotted spoon, carefully transfer the seafood and as many vegetables as you can to individual bowls. Discard the parsley stem bundle.

Return the broth in the pot to a boil, then reduce to a simmer. Add the lemon aioli, whisking constantly to combine, then cook, whisking constantly, until the broth thickens slightly, 1 to 3 minutes. Remove from the heat, stir in half the parsley leaves, and season to taste with salt and pepper.

Ladle the broth over the seafood and vegetables in the bowls. Garnish with the remaining parsley leaves and as much of the remaining piment d’Espelette as you like. Serve the ciabatta toasts alongside.