Yes, there is butter in the sauce, but the key ingredient is verjus. If you can't find it, use half white wine and half unseasoned rice vinegar.
Recipe information
Yield
Makes 4 servings
Ingredients
Lentils:
Verjus beurre blanc:
Trout and assembly:
Preparation
For lentils:
Step 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.
Step 2
DO AHEAD: Lentils can be cooked 1 day ahead. Let cool; cover and chill.
For verjus beurre blanc:
Step 3
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.
Step 4
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.
For trout and assembly:
Step 5
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.
Step 6
Stir parsley into verjus beurre blanc just before serving. Serve fish with lentils and sauce.