Fish Pie

Ingredients

• 6 tablespoons unsalted butter
• 4 cups whole milk
• 1 tablespoon kosher salt
• 0.5 teaspoon black pepper
• 4 large eggs
• 2 pounds russet potatoes – peeled and cut into chunks
• 1 small yellow onion – halved
• 2 leaves bay leaves
• 12 ounces white fish fillets
• 8 ounces smoked haddock fillets
• 12 ounces salmon fillet
• 0.25 cup all-purpose flour
• 0.25 cup fresh parsley – finely chopped

Instructions

1. Heat the oven to 400°F. Organize ingredients: cut the unsalted butter into pieces, reserving 2 tablespoons for the mash and 4 tablespoons for the sauce; warm the whole milk in a medium pot until steaming, then keep over the lowest heat; measure 1 tablespoon kosher salt and 0.5 teaspoon black pepper to use as directed, adding 2 teaspoons of the measured salt to the potato water later and using the rest to season the sauce and mash.
2. Place the large eggs in a small saucepan, cover with cold water by 1 inch, bring to a boil, then cover, remove from heat, and let stand 9 minutes; drain, run under cold water to cool, peel, and quarter.
3. Put the russet potatoes in a large pot, cover with cold water by 1 inch, add 2 teaspoons of the measured salt, bring to a boil, then simmer until tender when pierced, 12–15 minutes; drain and let steam-dry in the pot.
4. Slide the yellow onion and bay leaves into the warm milk, then nestle in the white fish fillets, smoked haddock fillets, and salmon fillet; bring just to a bare simmer over medium-low heat and poach until the fish is opaque and flakes but still moist, 5–7 minutes; lift the fish onto a plate with a slotted spoon, strain the poaching milk, reserving 2 cups for the sauce and up to 0.5 cup for the mash; discard the aromatics; when cool enough to handle, flake the fish into large bite-size pieces, discarding any skin or bones.
5. In a medium saucepan over medium heat, melt the 4 tablespoons reserved butter, whisk in the all-purpose flour, and cook, whisking, 2 minutes; gradually whisk in the 2 cups reserved poaching milk until smooth, then simmer, whisking often, until thick enough to coat the back of a spoon, 3–5 minutes; stir in the fresh parsley and most of the remaining measured salt and the measured pepper, tasting and adjusting seasoning.
6. Gently fold the flaked fish and the quartered eggs into the sauce, keeping the pieces chunky; scrape the mixture into a 2 to 2.5 quart baking dish and smooth the surface.
7. Return the drained potatoes to the empty pot, add the 2 tablespoons reserved butter, and mash, adding enough of the reserved poaching milk (up to 0.5 cup) to make a soft, spreadable mash; season with the last pinch of the measured salt if needed.
8. Spoon the mash over the filling, spreading to the edges and roughing up the top with a fork; set the dish on a rimmed sheet pan and bake until the filling is bubbling at the edges and the peaks of the topping are golden in spots, 25–30 minutes; let stand 10 minutes before serving.