👨‍🍳 Instructions

1. 1

   Preheat oven to 190°C (170°C fan/Gas Mark 5). Place the diced potatoes in a saucepan, cover with cold water, add a pinch of salt, and bring to a boil. Cook for 10-12 minutes until tender but not falling apart. Drain well and set aside.

   💡 Tip: Par-boiling the potatoes ensures they cook through in the pie without becoming mushy.
2. 2

   While the potatoes are cooking, melt 50g butter in a large saucepan or oven-safe skillet over medium heat. Add the sliced leeks and cook gently until softened, about 5-7 minutes.

   💡 Tip: Sweating the leeks brings out their natural sweetness.
3. 3

   Stir in the flour and cook for 1 minute, stirring constantly, to make a roux. Gradually whisk in the milk and fish stock until smooth. Bring to a simmer, stirring, until the sauce thickens.

   💡 Tip: Whisking continuously prevents lumps from forming in the sauce.
4. 4

   Gently stir in the fish chunks, cooked potatoes, chopped dill, parsley, and lemon juice. Season generously with salt and pepper. If using a separate pie dish, transfer the mixture to it now.

   💡 Tip: Be careful not to break up the fish too much when stirring.
5. 5

   For the topping, combine rolled oats, grated cheddar cheese, and the cold cubed butter in a bowl. Rub the mixture together with your fingertips until it resembles coarse breadcrumbs. Season with a little salt and pepper.

   💡 Tip: The oat topping provides a lovely crunchy contrast to the creamy filling.
6. 6

   Evenly scatter the oat and cheese topping over the fish and potato mixture. Place the pie dish on a baking sheet to catch any potential spills.

   💡 Tip: A baking sheet makes it easier to handle the hot pie dish and clean up.
7. 7

   Bake for 25-30 minutes, or until the topping is golden brown and crisp, and the filling is bubbling. Let the pie stand for 5-10 minutes before serving.

   💡 Tip: Allowing the pie to rest helps the filling to set slightly.