Mix the 1 tablespoon of milk and cornflour together and set aside.
Add the potatoes to a pan of boiling water and simmer for 12-15 minutes.
Put 250ml of milk in to a pan and put the salmon, haddock, prawns and parsley in to it. Bring the milk to the boil and then simmer for 5 minutes.
240 g salmon, 220 g smoked haddock, 150 g prawns, 250 ml milk, 10 g fresh parsley
Using a slotted spoon, lift the fish out and place in a large baking dish. Mix round so the fish flakes up.
Stir the cornflour mix and add to the milk with the sweetcorn, leek, cream cheese and a pinch of sea salt and black pepper. Mix until the cream cheese melts.
130 g sweetcorn, 1 leek, 150 g cream cheese
Drain the potatoes and mash them with the Dijon mustard and butter.
Pour the milk mixture over the fish and stir to distribute everything evenly.
Top with the mashed potatoes and sprinkle with the cheddar.
Put in the oven at 200°C/400°F/Gas 6 for 30-40 minutes. Put under the grill for 5 minutes to crisp the top.
Video
Notes
To save time, you can buy a packet of fish pie mix from the supermarket. Just make sure that this is fully defrosted before following this recipe.
If your creamy sauce isn't thick enough, then you can add a teaspoon of cornflour to thicken it up a little.
You can make an extra crispy topping by sprinkling a mixture of panko breadcrumbs and grated cheddar on top of the mashed potato/cauliflower mix.
You could make a basic cheese sauce and use that instead.
Add some extra flavour to the sauce with a little glug of white wine.