British Fish Pie with Mashed Potato Topping

Step 1
Place cubed potatoes into a large pot and cover with salted water; bring to a boil. Reduce heat to medium-low and simmer until tender, about 15 minutes. Drain.

Step 2
Transfer potato cubes to the bowl of a stand mixer. Blend gently, adding cubed butter and milk. Add in eggs and mix only until mashed potatoes reach your desired consistency, or finish by hand if needed;overmixing will yield gluey potatoes. Season with salt and pepper.

Step 3
Preheat the oven to 400 degrees F (200 degrees C).

Step 4
While potatoes are boiling, heat butter and olive oil in a large skillet over medium heat. Add onion and thyme and saute until onions are soft and browned, about 5 minutes. Deglaze with vermouth and cook until alcohol has evaporated, about 2 minutes. Whisk in flour. Slowly whisk in stock and milk and bring to a simmer. Simmer for 1 to 2 minutes. Sauce should be fairly thick, but if it's too thick you can thin it out with a little bit of additional stock. Taste and season with salt and pepper if desired. Turn off heat and stir in the half-and-half and parsley.

Step 5
Scatter salmon, cod pieces, and shrimp onto the bottom of a 2-quart baking dish. Sprinkle lightly with salt and pepper. Drizzle lemon juice over the top of the seafood.

Step 6
Pour prepared sauce over seafood and stir gently to combine. Spread prepared potatoes over the top and fluff with a fork, then sprinkle Cheddar cheese over the top.

Step 7
Bake in the preheated oven for 10 minutes. Reduce heat to 350 degrees F (175 degrees C) and bake until potatoes are evenly browned all over, seafood is cooked through, and pie is bubbly and piping hot, about 20 more minutes.

Step 8
Remove from the oven and allow to rest for 10 minutes before serving.