Pre-heat the oven to 190°C/375°F/gas mark 5. Place a pan of lightly salted water on the hob to boil. Peel the potatoes and cut them into 3cm² chunks. Place them in the pan and simmer for around 10 minutes until soft.
1 kg potatoes
Place the kale in a steamer and steam over the top of the potatoes for the last 5 minutes.
80 g kale
Drain the potatoes and mash, add a little milk or butter to soften if you like then leave to one side. Meanwhile, heat the milk in a large pan and add the fish. Bring the milk to a boil then turn down the heat and simmer for 6 - 7 minutes.
750 ml milk, 250 g smoked haddock, 200 g white fish fillets
Heat the butter in a large pan and gently fry the leeks for 4 - 5 minutes until soft, but not brown.
50 g butter, 360 g leeks
Remove the fish from the pan and set it aside to cool. Pour the milk into a jug. Top tip. Put your milk pan into a bowl of hot water immediately, or it can be a pain to clean.
Add the flour to the leeks and stir well. Over a low heat, gradually add all the milk, stirring all the time. Season with salt and freshly ground black pepper.
3 tablespoon plain flour
Carefully break the fish into chunks, leaving behind the skin, and stir into the sauce. Add the prawns, peas, kale, and lemon zest.
100 g prawns, 100 g frozen peas, 1 lemons
Place it all in an ovenproof dish, and cover it with the mashed potatoes using a fork to spread it evenly. Start at the edges of the dish and work in towards the middle. Bake in the oven for 25 minutes.
You can use any fish in a fish pie. Try a combination of white fish and smoked or oily fish. You could also just use one type if you prefer. A fish pie mix is convenient, but buying the fish separately is usually better value.
Other vegetables you could use include cabbage, spinach, broccoli, and sweetcorn.
The best potatoes to use for mash are Desiree or Maris Piper potatoes in the UK and Russets or Yukon Gold in the US. These are higher starch potatoes and will give a light fluffy mash. Waxy potatoes are more difficult to mash and you can end up with a potato paste rather than a fluffy mash. You could also try using sweet potatoes instead or half and half.
To make sure your mash doesn't sink into the filling, let your cooked potatoes steam for a few minutes. This helps dry them out a little. Watery potatoes weigh heavily and will seep into the filling. When adding the mashed potatoes, use a dessert or tablespoon and spoon it on one spoonful at a time. Start at the edges and work inwards towards the middle. Once you've covered the filling, you can go over the top with a fork to make a pattern or little grooves in the potato that will crisp up nicely in the oven.
Storing and Reheating
To reheat fish pie, cover with foil and reheat in the oven at 180C/350F/Gas Mark 4 for around 40 minutes until piping hot. To reheat from frozen allow around 1 ½ hours.
Fish pie can be frozen for up to 3 months. It can be frozen once assembled, without being cooked in the oven. If your fish pie has not already been cooked, leave it uncovered when reheating to allow it to brown on the top.
It can be stored cooked in the fridge for 2 - 3 days. You can also assemble it up to 48 hours in advance and keep it in the fridge.