Seafood en Brodo with Tarragon Pesto

Ingredients

• 2  bay leaves 
• 2 teaspoons peppercorns black
• 8 slices bread country-style toasted
• 8 ounces carrots chopped
• 3.5 pounds cockles scrubbed
• 1 cup mirin dry
• 4  fennel bulb chopped
• 4 pounds fish fillet 
• 32 ounce fish fillet firm (such as halibut, snapper, or cod)
• 8  parsley fresh
• 1 cup parsley fresh
• 0.5 cup tarragon fresh
• 1  garlic clove chopped
• 4  garlic clove thinly sliced
• 8 servings pepper freshly ground
• 2  leek white halved lengthwise thinly sliced
• 4  lemon zest with a vegetable peeler
• 0.3 cup olive oil extra virgin extra-virgin
• 0.5 cup olive oil divided
• 8 servings olive oil (for drizzling)
• 4 medium onion chopped
• 1 teaspoon saffron threads 

Equipment

• food processor
• bowl
• baking sheet
• ladle
• oven
• pot
• sieve
• plastic wrap
• aluminum foil

Directions

1. Preheat oven to 450F. Divide bones, onions, fennel, carrots, and 1/4 cup oil between 2 rimmed baking sheets; season with salt and pepper and toss to coat. Roast, tossing halfway through, until vegetables are softened and browned, 6075 minutes.
2. Heat saffron and remaining 1/4 cup oil in a large pot over medium-high heat, stirring, until fragrant, about 2 minutes.
3. Add leeks and garlic; season with salt and pepper and cook, stirring often, until golden, 810 minutes.
4. Add vermouth; bring to a boil, reduce heat, and simmer, stirring occasionally, until slightly reduced, about 3 minutes.
5. Add roasted bones and vegetables, parsley stems, lemon zest, bay leaves, peppercorns, and 10 cups water to pot. Bring to a boil, reduce heat, and simmer gently, skimming as needed, until reduced by half, about 1 hour. Strain through a sieve into a clean pot; discard solids. Season with salt.
6. Pulse garlic, parsley, and tarragon in a food processor until very finely chopped. With motor running, slowly add oil, and process until smooth; season with salt and pepper.
7. Return broth to a simmer; add shellfish, cover pot, and cook until shellfish open (discard any that do not open), about 5 minutes.
8. Transfer shellfish to a large bowl and add a ladleful of broth; tent with foil. Season fish with salt and pepper; add to broth in pot. Cover; cook fish gently until opaque throughout, about 4 minutes.
9. Divide fish and shellfish among shallow bowls and ladle broth over.
10. Drizzle stew with oil, top with pesto, and serve with toast.
11. DO AHEAD: Brodo can be made 3 days ahead. Cover and chill. Pesto can be made 1 day ahead. Press plastic wrap directly on surface and chill.