- Kosher or sea salt
- 1 cup tightly packed fresh flat-leaf parsley leaves, plus 2 tablespoons minced fresh parsley
- 3 tablespoons water, plus ¼ cup
- 3 large russet potatoes (about 2 pounds total), peeled and quartered
- 4 salmon fillets (about 6 ounces each), skin and pin bones removed
- 2 tablespoons olive oil
- ¼ teaspoon cayenne pepper
- 1 cup (2 sticks) unsalted butter
- 2/3 cup milk, warmed
- Freshly ground pepper
- 1 teaspoon minced garlic
- Fill a 2-quart saucepan two-thirds full of water and bring to a boil over high heat. Add 1 teaspoon of salt to the boiling water and then add the 1 cup parsley. Cook just until tender and bright green, about 1½ minutes. Drain the parsley in a sieve. Run cold water over the parsley until it is cool. Squeeze the parsley to remove the excess water. Place in a blender, add the 3 tablespoons water, and blend until puréed. Transfer to a small bowl and set aside.
- Place the potatoes in a large saucepan and cover with cold water. Partially cover the pot and bring to a boil over high heat. Add 1 teaspoon of salt and reduce the heat so the water boils gently. Cook until the potatoes are tender when pierced with a knife, 12, to 15 minutes.
- Meanwhile, preheat the oven to 250°F. Arrange the salmon on a rimmed baking sheet lined with parchment paper. Rub each fillet with olive oil and sprinkle lightly with a little salt and cayenne pepper. Set aside. Melt ½ cup of the butter in a small sauté pan. Set aside and keep warm.
- When the potatoes are tender, place the salmon in the oven to bake and set a timer for 20 minutes. Drain the potatoes in a colander. Using a ricer or potato masher, mash the potatoes. Stir the melted butter into the potatoes and then gradually add the milk Beat until smooth and creamy. Add salt and pepper to taste. Cover and keep warm.
- While the salmon is baking, bring the ¼ cup water to a boil in the sauté pan you used to melt the butter. Reduce the heat to low. Cut the remaining ½ cup butter into 4 pieces and, using a whisk, stir the butter into the water a chunk at a time. Stir in 2 tablespoons of the parsley purée, the garlic, ¼ teaspoon of salt, and a couple of grinds of pepper. Taste and adjust the seasoning. Set aside and keep warm.
- Check the salmon. The salmon is done when the fat between the layers begins to turn whitish and opaque and the fish flakes slightly. An instant-read thermometer inserted in the center should register 125° to 130°F. When salmon is cooked gently at such a low temperature the fish looks underdone because the color is so beautifully pink and vivid, but it is fully cooked.
- To serve, place a portion of mashed potatoes in the center of warmed dinner plates or shallow pasta bowls. Top with a piece of salmon and drizzle some of the sauce around each plate. Garnish with a little minced parsley and serve immediately.