In a pan place the fish, onion, bay leaves and enough milk to cover the fish. Bring to the boil, take off the heat and allow to poach for 2 mins until the fish is just cooked.
Strain over a bowl, reserving the milk and flake the fish into 3-4cm pieces and place in your pie dish.
Take 25g of butter and melt in a pan over a medium heat. Add the flour, cook out slowly stirring all the while and gradually add the reserved poaching milk to make a béchamel. Whisk quickly as you add the milk to avoid any lumps.
Once at a lovely smooth consistency, add Worcestershire sauce, both mustards and chopped parsley.
Build the pie by adding your quartered eggs to the fish in your pie dish, cover with plenty of sauce and allow to cool whilst getting on with your mash.
Take the milk, cream, thyme and garlic and warm in a saucepan. Bring to just before simmering point, take off the heat and allow to infuse for around 20-30 minutes.
Peel and halve your potatoes, bring to the boil in a saucepan and simmer until tender. Once cooked, drain thoroughly and mash, gradually adding the warm milk and butter a little at a time, until you have a smooth consistency. Season with ground black pepper and salt to taste.
Either pipe or fork on the mash to the top of your fish pie mixture. Finish with your grated cheese and bake for a further 20-25mins, until piping hot throughout and golden brown. Delicious with peas!