Evening Meal on the Thames: British Fish Pie

This British fish pie makes a comforting evening meal on the Thames: flaky white fish, salmon, and smoked haddock sit in a creamy leek sauce beneath a golden mashed-potato topping. Fish pie is a familiar British home-cooked dish with many regional and family variations, and this version is hearty enough for supper without being difficult to prepare.

Ingredients

2 lb (900 g) floury potatoes, peeled and cut into 1-inch (2.5 cm) chunks
4 tbsp (57 g) unsalted butter, divided
⅓ cup (80 ml) whole milk, for the mashed-potato topping
1 tbsp (15 ml) neutral oil
1 medium leek (about 5 oz / 150 g), white and light-green parts thinly sliced and rinsed well
2 tbsp (16 g) all-purpose flour
1¾ cups (420 ml) whole milk, for the sauce
½ cup (120 ml) fish stock or low-sodium vegetable stock
1 tsp (5 g) Dijon mustard
¼ tsp (0.5 g) ground nutmeg
1 tbsp (15 ml) lemon juice
1 lb (450 g) skinless cod or haddock, cut into 1-inch (2.5 cm) pieces
8 oz (225 g) skinless smoked haddock, cut into 1-inch (2.5 cm) pieces
8 oz (225 g) skinless salmon, cut into 1-inch (2.5 cm) pieces
1 cup (150 g) frozen peas
¼ cup (15 g) chopped fresh flat-leaf parsley
½ tsp (3 g) fine salt, plus more for the potato water
¼ tsp (0.5 g) freshly ground black pepper
½ cup (50 g) finely grated mature cheddar, optional, for the potato topping

Instructions

Heat the oven to 400°F (200°C). Set a rack in the middle of the oven and lightly butter a 2-quart (1.9 L) baking dish. If the fish is frozen, thaw it completely in the refrigerator and pat it dry before cutting; excess water can thin the sauce.
Put the potatoes in a large saucepan and cover with cold water by about 1 inch (2.5 cm). Add a generous pinch of salt. Bring to a boil, then reduce the heat to maintain a steady simmer. Cook for 18 to 20 minutes, until a knife slips into the largest pieces easily. Drain thoroughly and let the potatoes steam-dry in the hot pan for 1 minute.
While the potatoes cook, make the sauce. Warm the oil and 1 tablespoon (14 g) of the butter in a saucepan over medium heat. Add the sliced leek and cook for 5 to 6 minutes, stirring often, until soft but not browned. If the pan looks dry, lower the heat rather than letting the leek catch; browned leek can make the sauce taste bitter.
Sprinkle the flour over the leek and stir for 1 minute so it coats the vegetables. Gradually whisk in the 1¾ cups (420 ml) milk and the stock, adding a little at a time to keep the sauce smooth. Bring it to a gentle simmer and cook for 3 to 4 minutes, stirring, until it lightly coats a spoon. Stir in the mustard, nutmeg, lemon juice, salt, and pepper. Take the pan off the heat and fold in the peas and parsley.
Mash the drained potatoes with the remaining 3 tablespoons (43 g) butter and ⅓ cup (80 ml) milk. Season to taste. The mash should be soft enough to spread but not runny; add another tablespoon of milk only if it still feels stiff. Fold in the cheddar if you want a richer, more browned topping.
Arrange the cod, smoked haddock, and salmon evenly in the prepared baking dish. Pour the leek sauce over the fish and gently nudge the pieces so sauce reaches the bottom and sides. Spoon the mashed potatoes over the filling, spread them to the edges to seal in the sauce, and rough up the surface with a fork. A few ridges help the top brown.
Bake for about 30 minutes, until the topping is golden and the filling bubbles at the edges. Check a thick piece of fish in the center with a food thermometer: the USDA FSIS safe minimum internal temperature for fish is 145°F (63°C). If the potatoes brown before the fish is ready, loosely cover the dish with foil and continue baking until the fish reaches that temperature. Rest the pie for 5 minutes before serving so the sauce settles and the first portions hold together.

Tips

Rinse the sliced leek carefully. Grit often hides between its layers, and even a little can spoil the smooth texture of the filling. Swirl the slices in a bowl of cold water, lift them out, and leave the grit behind rather than pouring the water through them.
Use fish pieces of similar size so they cook at roughly the same rate. If you use a particularly thin fillet, cut it into larger chunks; small pieces can become dry before the potato topping has browned. The thermometer check is more reliable than judging by color alone.
Smoked haddock adds a distinct savory, smoky flavor, but it can be hard to find. Replace it with the same weight of fresh cod or haddock and add a small pinch of salt; the pie will taste milder and less smoky. Taste the sauce before adding extra salt because smoked fish varies in saltiness.
For a smooth sauce, add the milk gradually and whisk as you pour. If a few small lumps form, whisk firmly off the heat before adding the fish. Avoid boiling the sauce hard; a gentle simmer thickens it without scorching the milk.

Serving Suggestions

Serve the pie hot, with a broad spoon so each portion includes both the crisp potato top and plenty of sauce. A green vegetable makes a useful contrast: try steamed green beans, broccoli, or cabbage, or serve a simple salad dressed with lemon and a little oil. The filling is rich, so keep sides lightly seasoned and avoid adding another heavy cream sauce.

If you are planning a relaxed supper, assemble the table while the pie rests for five minutes. Put lemon wedges and extra chopped parsley alongside it for anyone who wants a fresher finish. Crusty bread is optional; it is particularly handy for catching the last of the leek sauce. For a smaller meal, serve a modest portion with a crisp salad rather than increasing the potato topping.

Variations

Change the fish to suit what is available, keeping the total amount close to 2 lb (900 g). Pollock, hake, or additional haddock work in place of cod, and you can use all white fish if you do not want salmon. Keep at least some smoked fish for the traditional smoky note, or omit it and season the sauce carefully for a gentler flavor. Fish counters may sell mixed pie fish, but check that the pieces are boneless and cut them to a similar size.

For a vegetable-forward pie, replace up to half the fish with sliced, sautéed mushrooms or extra peas and leeks. Those additions release moisture, so cook mushrooms until their liquid has evaporated before adding them. For a sharper topping, use mature cheddar; for a more classic, simple finish, leave out the cheese and add a little extra butter to the mash. Chopped chives can stand in for parsley, though they give the filling a mild onion flavor.

You can also make individual pies in oven-safe dishes. Divide the filling and topping between six dishes, leaving room for the sauce to bubble, and begin checking them after about 20 minutes. Their cooking time depends on the size and material of the dishes, so use the same thermometer check for the fish rather than relying on the shorter estimate alone.

Storage and Reheating

Refrigerate leftovers within 2 hours of baking, in a covered container or covered baking dish. They keep for 3 to 4 days in the refrigerator. For quicker, more even reheating, portion the pie into shallow containers; avoid leaving a large dish on the counter to cool for an extended period.

Reheat individual portions in a microwave, stirring or turning the filling partway through if possible, or warm them in an oven at 350°F (175°C) until hot throughout. Reheat leftovers to 165°F (74°C), checked in the center with a food thermometer. A covered portion helps keep the fish from drying; uncover it briefly at the end if you want the potato topping to crisp again. You can freeze portions in airtight freezer-safe containers for up to 2 months for best quality. Thaw in the refrigerator before reheating, and do not reheat the same portion repeatedly.

Frequently Asked Questions

Can I prepare fish pie ahead of time?
Yes. Make the sauce and mash, assemble the pie with thawed, dry fish, cover, and refrigerate promptly. For best texture, bake it the same day or within 24 hours. Because it starts cold, it may need extra oven time; check that the center of the fish reaches 145°F (63°C) rather than assuming the stated baking time will be exact.

Can I use frozen fish?
Yes, but thaw it fully in the refrigerator first and pat it dry. Fish added while still frozen can release water into the filling and make it difficult to tell whether the center is cooked. Do not thaw fish on the counter. If it has been thawed in the refrigerator, use it promptly and follow any safe-handling instructions on its packaging.

How can I tell when the fish pie is done?
The topping should be golden and the sauce should bubble at the edges, but appearance alone cannot confirm that the center fish is safely cooked. Insert a food thermometer into a thick piece in the middle of the dish; fish should reach 145°F (63°C). If it has not reached that temperature, return the pie to the oven and check again after a few minutes.

Can I make the topping without dairy?
For a dairy-free version, use an unsweetened plant-based milk and dairy-free butter in both the sauce and mash. Choose a milk with a neutral flavor, and check that it is suitable for cooking. The sauce may thicken differently, so simmer it until it coats a spoon and add a little more flour mixed with cold milk if needed. Leave out the cheddar or use a dairy-free alternative.

Why did my fish pie turn watery?
Common causes are fish that was not thawed and dried, vegetables that released extra liquid, or sauce that was too thin before baking. Simmer the sauce until it coats a spoon, pat thawed fish dry, and cook any watery vegetables before adding them. Letting the finished pie rest for five minutes also gives the sauce time to settle before serving.

More recipes to cook

Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes

Spotted an error? Tell us and we will correct it (corrections policy).