Ingredients

• 2 tablespoons olive oil
• 1 small carrot, peeled, finely chopped
• 1 celery stalk, finely chopped
• 1/2 small onion, finely chopped
• 2 garlic cloves, finely chopped
• 1 cup black beluga lentils or French green lentils
• 2–3 cups low-sodium chicken broth
• 2 teaspoons Sherry vinegar
• Kosher salt, freshly ground pepper
• 1 small shallot, thinly sliced
• 1 garlic clove, peeled, crushed
• 1 whole star anise pod
• 1 bay leaf
• 6 black peppercorns
• 1 cup white verjus
• 1/2 cup dry white wine
• 1/2 cup (1 stick) chilled unsalted butter, cut into pieces
• 1 tablespoon chopped fresh tarragon
• 1 tablespoon fresh lemon juice
• Kosher salt, freshly ground pepper
• 2 tablespoons olive oil
• 4 6-ounce skin-on steelhead trout or salmon fillets
• Kosher salt, freshly ground pepper
• 1 tablespoon unsalted butter
• 2 tablespoons chopped fresh flat-leaf parsley
• Ingredient info: Verjus is a tart juice made from unripe grapes. Find it at specialty foods stores and online.

Instructions

1. Heat oil in a large saucepan over medium-high heat. Add carrot, celery, onion, and garlic and cook, stirring often, until softened, 5–8 minutes. Mix in lentils and add broth to cover by 1". Bring to a boil; reduce heat, cover, and simmer, adding more broth as needed to keep lentils covered, until lentils are tender, 20–30 minutes. Mix in vinegar; season with salt and pepper. Cover and set aside; keep warm.
2. DO AHEAD: Lentils can be cooked 1 day ahead. Let cool; cover and chill.
3. For verjus beurre blanc: Bring shallot, garlic, star anise, bay leaf, peppercorns, verjus, and wine to a boil in a medium saucepan and cook until reduced to 1/4 cup, 15–20 minutes. Strain through a fine-mesh sieve into a small saucepan; discard solids. Place saucepan over low heat and gradually whisk in butter, until butter is melted and sauce is emulsified. Whisk in tarragon and lemon juice; season with salt and pepper. Cover and set aside; keep warm.
4. Bring shallot, garlic, star anise, bay leaf, peppercorns, verjus, and wine to a boil in a medium saucepan and cook until reduced to 1/4 cup, 15–20 minutes. Strain through a fine-mesh sieve into a small saucepan; discard solids.
5. Place saucepan over low heat and gradually whisk in butter, until butter is melted and sauce is emulsified. Whisk in tarragon and lemon juice; season with salt and pepper. Cover and set aside; keep warm.
6. For trout and assembly: Heat oil in a large nonstick skillet over medium-high heat. Season fish with salt and pepper. Place fish, skin side down, in pan and cook, undisturbed, until skin is crisp and releases from pan, about 4 minutes. Turn fish, add butter to pan, and cook, tilting pan and spooning butter over fish, until opaque throughout, about 2 minutes longer. Stir parsley into verjus beurre blanc just before serving. Serve fish with lentils and sauce.
7. Heat oil in a large nonstick skillet over medium-high heat. Season fish with salt and pepper. Place fish, skin side down, in pan and cook, undisturbed, until skin is crisp and releases from pan, about 4 minutes. Turn fish, add butter to pan, and cook, tilting pan and spooning butter over fish, until opaque throughout, about 2 minutes longer.
8. Stir parsley into verjus beurre blanc just before serving. Serve fish with lentils and sauce.