COOK POTATOES: Cook the potatoes in plenty of salted water until tender. Drain, mash, then beat in the milk and butter until smooth. Season to taste with salt and pepper then set aside. Heat oven to 200°C / 400°F / Gas 6.

POACH FISH: Place fish in a saucepan in one layer. Pour over the milk, add the bay leaf, then season with salt and pepper. Cover and bring to a simmer, then turn the heat right down to low and simmer for 4-5 minutes.

SAUTÉ LEEK: Strain the fish, reserving the milk. Flake the fish into large chunks. Rinse the saucepan and wipe it dry, then heat 25g of the butter until bubbling. Cook the leek for 2-3 minutes, just until softened, then remove with a slotted spoon.

MAKE WHITE SAUCE: Melt the remaining butter and flour together in the same saucepan. Allow to cook, stirring all the time, for 3 minutes. Pour in the milk and white wine, beating until smooth. Add the cream and mustard and cook until thick. This will take around 10 minutes, make sure to stir from time to time to prevent the sauce from catching. Season with salt and pepper.

COMBINE INGREDIENTS: Add fish, prawns (shrimp) and parsley, stir to combine and remove from heat. Pour into the baking dish and spoon over the mashed potato, spreading it out to cover the filling.

BAKE: Place on a baking tray (this is important! Fish pie bubbles over 100% of the time!) and bake in the preheated oven 40-45 minutes until golden and beginning to crisp on the top. Allow to cool for five minutes before serving.