For the mustard-herb butter:
- 5 tablespoons unsalted butter, softened
- 1 tablespoon chopped chives
- 1 teaspoon chopped tarragon
- 2 teaspoons grainy mustard
- 2 teaspoons fresh lemon juice
For the lentils:
- 1 cup French green lentils
- 4 cups water
- 2 medium leeks (white and pale green parts only)
- 1 tablespoon unsalted butter
- 1/2 to 1 tablespoon fresh lemon juice
For the salmon:
- 4 (6-ounce) pieces skinless salmon fillet
- 2 tablespoons unsalted butter
To make the mustard-herb butter, stir together all of the ingredients with 1/4 teaspoon each of the salt and pepper. The mustard-herb butter can be made 1 day ahead and chilled, covered. Soften it at room temperature before using (1 hour).
Bring the lentils, water, and 3/4 teaspoon salt to a boil in a heavy medium saucepan, then reduce the heat and simmer, uncovered, until the lentils are just tender, 20 to 25 minutes. Remove from the heat and let stand 5 minutes. Reserve 1/2 cup of the cooking liquid, then drain the lentils.
While lentils cook, chop and wash the leeks. Cook the leeks in the butter in a heavy medium skillet over medium-low heat, stirring occasionally, until softened, 6 to 8 minutes.
Add the lentils with the reserved cooking liquid to the leeks along with 3 tablespoons of the mustard-herb butter and cook, stirring, until the lentils are heated through and the butter is melted. Add the lemon juice and salt and pepper to taste. Remove from the heat and keep warm, covered. The lentils can be cooked (but not drained) 1 day ahead and chilled in the cooking liquid, covered (once cool).
While the leeks cook, sauté the salmon. Pat the salmon dry and sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper (total). Heat the butter in a large nonstick skillet over medium-high heat until the foam subsides, then sauté the salmon, turning once, until it's golden and just cooked through, 6 to 8 minutes total. Serve the salmon, topped with the remaining mustard-herb butter, over the lentils.
- Yields: 4 servings
- Preparation Time: 50 minutes