Recipe Details

Ingredients

• 3 lb. 

  Yukon gold potatoes, peeled and cut into 1/2" pieces

• Kosher salt

• 1/2 c. 

  (1 stick) plus 6 tbsp. unsalted butter, divided

• 1/2 c. 

  heavy cream, divided

• Freshly ground black pepper

• 1 

  large leek, scrubbed, white and light green parts sliced into 1/4" slices

• 1 

  stalk celery, sliced

• 2 

  cloves garlic, finely chopped

• 1 tsp. 

  dried oregano

• 2 tbsp. 

  all-purpose flour

• 1 1/2 c. 

  low-sodium chicken or fish stock

• 1 

  large egg yolk

• 1 

  lemon, juiced

• 1/3 c. 

  fresh dill, plus more for serving

• 1/3 c. 

  frozen peas

• 1 1/2 lb. 

  salmon, shrimp, cod, or haddock, cut into bite-size pieces

Description

1. Step 1Place potatoes in a large pot and cover with cold water; season with 1 tablespoon salt. Bring to a boil, then reduce heat to medium-low and simmer until potatoes are tender, 18 to 20 minutes.
2. Step 2Drain potatoes and return to pot. Mash with a potato masher or food mill. Cut 1/2 cup (1 stick) butter into large pieces, then add to potatoes. Add 1/4 cup cream and stir to combine; season with salt and pepper.
3. Step 3Arrange a rack in center of oven; preheat to 425°. In a large, ovenproof skillet over medium heat, melt 2 tablespoons butter. Add leek and celery and cook, stirring occasionally, until softened and just beginning to turn golden on the edges, 6 to 8 minutes. Add garlic and oregano and cook, stirring, until fragrant, about 1 minute more. Sprinkle with flour and mix to combine. Cook, stirring occasionally, until flour has slightly toasted and you can no longer smell raw flour, 1 to 2 minutes.
4. Step 4Whisk in stock and remaining 1/4 cup cream and bring to a boil. Immediately reduce heat to medium-low, bring to a simmer, and cook, stirring occasionally, until slightly thickened, 5 to 6 minutes.
5. Step 5In a small bowl, whisk egg yolk and lemon juice. To temper, add 1 tablespoon stock mixture and stir to combine, then continue to add more stock 1 tablespoon at a time until mixture is smooth.
6. Step 6Add yolk mixture to skillet and stir to combine. Fold in dill and peas. Cook, stirring occasionally, until peas are warmed through, about 3 minutes; season with salt and pepper. Remove from heat.
7. Step 7Season fish with salt and pepper, then fold fish into sauce. Cover fish mixture with mashed potatoes, then make ridges in potatoes with a fork. Cut remaining 4 tablespoons butter into small pieces and sprinkle over potatoes.
8. Step 8Place skillet on a baking sheet (to avoid any bubbling over). Bake fish pie until potatoes are lightly golden brown, 20 to 25 minutes.
9. Step 9Let pie set 10 minutes. Top with more dill.