Step 1

Cut peeled potatoes into chunks.

Step 2

Place potatoes into a large pot of cold, salted water, ensuring that the potatoes are fully covered by the water by at least an inch or two above the potatoes. Bring to a boil and cook until fork-tender, about 15 minutes. Drain.

Step 3

Rice potatoes (or mash them) into a bowl. Add butter, milk, cheddar cheese, chives and salt, stirring to combine. Set aside.

Step 4

Heat olive oil in a 12-inch heavy oven-safe sauté/deep pan over medium heat on the stovetop.

Step 5

Add leek and cook, stirring often, for 5 minutes or until softened.

Step 6

Stir in garlic and cook for 1 minute.

Step 7

Add carrots, celery, and 1/4 teaspoon each of salt and black pepper. Cook, stirring often, for 8 to 10 minutes or until softened slightly.

Step 8

Add butter and melt.

Step 9

Stir in flour to form a paste. Cook for 2 to 3 minutes.

Step 10

Slowly (1/2 cup at a time) whisk in seafood broth and milk (you want to add the liquid in increments so that it gives things a chance to thicken before adding more liquid). Bring to a gentle simmer and cook until thickened, about 3 to 5 minutes.If you want less sauce in the finished product, you can add about 1/2 cup less broth here.

Step 11

Season with thyme, 1/2 teaspoon each of salt and black pepper, cayenne pepper, and lemon zest.

Step 12

Stir in peas.

Step 13

Season cod and salmon with remaining 1/2 teaspoon each of salt and pepper.

Step 14

Distribute seafood in pan, stirring to incorporate.

Step 15

Preheat oven to 350 degrees Fahrenheit.

Step 16

Top seafood with reserved cheesy mashed potatoes. Don't smooth out perfectly. Leave little bumps and valleys so they create character and some crispy bits when baked.

Step 17

Carefully place the pan onto a sheet pan (to catch any spills), then transfer to the preheated oven and bake for 40 to 45 minutes until everything is cooked through and the mashed potatoes have a little golden brown colour.

Step 18

Let the fish pie cool for about 30 minutes before serving (don't skip this as it allows things to settle). Garnish with thyme and chives, if desired. Delicious served with lemon wedges. Enjoy!