Cut your potatoes into 1" chunks. Boil your potatoes until soft enough for mashing. About 15 minutes.
Drain the potatoes and put back in the saucepan. Add the butter and cream.
Mash well until smooth. Set aside.
Preheat your oven to 200 C/400 F/Gas Mark 6
Place your fish in a small saucepan and add the 500 mls milk. You need a smallish saucepan so that the milk covers the fish.
Bring up to a simmer then cook for 60 seconds. Remove from the heat.
Drain the fish and collect the milk cooking liquid. I use a sieve. Empty the fish into your cooking dish. Set aside.
Melt the butter for the cheese sauce in a saucepan, I use the same one that I cooked the fish in. Add the flour.
Mix together and cook gently for a minute.
Swap to a whisk and add the milk and whisk it all until smooth. Bring to a simmer and keep whisking as the mixture thickens.It may look lumpy but keep whisking and the lumps will disappear.
Add the cheese and stir as it melts. I use a wooden spoon here just because it's easier as the cheese doesn't get stuck in the whisk.
Pour the cheese sauce over the fish.
Mix the two together gently.
Top with mash baby.
Place on an oven tray and bake for about 45 minutes until brown on top with crispy edges.
Apply To Cheesily Content Face