I used to make a pie with salmon,cod and haddock similar to this.
Off the top of my head:
Make/buy some pastry and line a pie dish.
Stick it in the fridge til needed.
Chop and fry a bunch of spring onions or shallots in butter slowly and on a medium to low heat.
When the onions soft and golden add the fish, nice big flakes.
Stir it about drop a bit of salt and pepper and add a pint of milk, turn up the heat.
In a bowl mix two egg yolks with a half cup of milk.
Add about 5 tablespoon of flour and mix well.
Add a few spoons of the hot milk to this to stop the eggs scrambling.
Add to the fish and milk mix.
Turn off the heat and let it cool.
Now mix the two egg yolks til you get peaks and fold it in.
Taste it and see if it needs salt pepper,parsley, dill etc
Add a handful of sharp cheddar and fill the pie dish.
You don´t have to put a top layer of pastry, but it´ll work either way.
Give it about half an hour at 180 degrees and 15 mins at 150degrees.
Last bit depends on your oven.
Peas,carrots etc optional just bung em in.