Fish Pie

Boil and mash the potatoes

Cut the peeled potatoes into even chunks and add to a large pot of well-salted cold water. Bring to a boil and cook for 15–18 minutes until completely tender when pierced with a knife. Drain thoroughly, then mash with half the butter until smooth and fluffy. Season generously with salt and white pepper, cover, and keep warm. While the potatoes cook, preheat your oven to 200°C (180°C fan / gas 6).

Build the white sauce

Melt the remaining butter in a medium saucepan over medium heat. Add the flour and stir constantly for 1–2 minutes to cook out the raw flour taste — it should look like a pale, sandy paste. Remove from the heat and gradually whisk in the milk, a splash at a time at first, until the mixture is completely smooth. Return to medium-low heat and stir continuously for 2–3 minutes until the sauce thickens enough to coat the back of a spoon. Season well with salt and freshly ground black pepper.

Add the fish and peas

Gently fold the cubed white fish, smoked haddock, and defrosted peas into the warm sauce — don't over-stir, as the fish will break up. The fish will finish cooking in the oven, so it just needs to be evenly distributed. Pour the filling into a deep baking dish (roughly 20×28 cm) and spread level.

Top with mash and bake

Spoon the mash over the filling and spread it to the edges with a fork, then use the fork to rough up the surface into peaks — these will catch and turn golden in the oven. Bake for 25–30 minutes until the top is golden and the filling is visibly bubbling around the edges. Leave to rest for 5 minutes before serving, which helps the filling set slightly for cleaner portions.