You can make this pie with any combination of white oily and smoked fish that you like. I used salmon, smoked haddock and sustainably-source cod, but you can use what is locally available. If you fancied you could also add prawns or other shellfish at the same time as you add the other fish.
Ingredients For the potato topping
1kg floury potatoes
Knob of butter
Splash of milk
For the fish sauce
200g firm-fleshed white fish
100g oily fish
100g smoked fish
1 tsp Dijon or English mustard
½ a 25g pack or a small bunch chives, finely snipped or a couple of teaspoons of dried chives
100g frozen peas or sweetcorn
100g grated hard cheese (like Cheddar)
Preheat the oven to 180 Celsius
Peel and halve the potatoes.
Bring a large pan of water to boil and then cook the potatoes until tender.
Drain the potataoes and then mash them with butter and a splash of milk. Set aside until the fish sauce is ready.
Melt the butter in another saucepan.
Add the flour and cook for a couple of minutes until it is a golden straw colour.
Chop the leeks finely, then add to the flour and butter. Cook gently for a few minutes until they start to soften.
Gradually whisk the milk into the buttery leeks, combining it as you do so into a smooth sauce.
Add the frozen peas (you could also add sweetcorn at this stage) and the chives.
Add the grated cheddar cheese and mustard and mix the sauce.
Cut the fish into bite-sized chunks then add to the sauce, mix well to combine, then put into a greased baking dish.
Spoon the mashed potato on top of the fish mix.
Scatter a little more cheese on top.
Bake in the oven for about 25 minutes. The sauce should be bubbling, and the cheese golden brown.