Place all fish, onion and bay leaves in a large saucepan. Add milk and simmer over a low heat for 5 to 10 minutes until the fish has just started to cook. Using a slotted spoon, transfer fish to a bowl and pour milk into a jug. Remove bay leaves and onions.
In another saucepan, heat butter, add flour whisking for 5-7 minutes until well combined and flour has cooked off. Slowly add the milk and cream mixture, whisking continuously, until you have a thick sauce. Remove from heat, season and add back in your fish and parsley. Spoon carefully into a pie dish. Preheat oven to 180°C.
To make the topping, boil potatoes whole in their skins. Cook until tender. Allow to cool and then pass through a sieve. To the sieved potatoes add milk and butter until smooth and creamy. Stir through cheese and sour cream until combined. You can either pipe the potato on or smooth over using a fork.
Bake for 30 minutes until top browns and the filling bubbles. Enjoy. PS. It's even better the next day.
Recipe by Eatin' mess at https://eatinmess.com.au/recipes/by-ingredient/seafood/fish-pie/