Preheat the oven to 220°C/Fan 200°C/Gas Mark 6. Peel the potatoes and cut into large, evenly sized chunks. Place in a large pan, add a pinch of salt and cold water to cover. Bring to the boil, cover and simmer for 15 minutes or until the potatoes are tender when tested with a fork.
Meanwhile, place the cubes of fish in a medium pan, cover with the milk, add the bay leaf and a good grind of fresh black pepper. Place over a gentle heat and slowly bring to the boil. Simmer for 2 minutes.
Carefully strain the milk from the fish and reserve it with the bay leaf still in. Arrange the fish over the base of a 1½ litre/2½ pint ovenproof dish and place on a baking tray.
Rinse out the medium pan, add the milk, 50g of butter and the flour. Place on a low heat and slowly bring to the boil, whisking with a balloon whisk all the time until the mixture comes to the boil and thickens. Cook for 1 minute, stirring occasionally.
Remove from the sauce from the heat and stir in half the cheese. Pour over the fish mixture.
Drain the potatoes in a colander, then when they are dry, return to the pan. Add the remaining butter and use a potato masher to mix to a smooth mash. Add the cheese, and seasoning to taste, and fluff up with a fork.
Use a fork and spoon to heap the potato over the fish mixture, leaving it rough and crumbly with a few gaps here and there. Bake in the hot oven for 20 mins or until the top is golden. Serve with peas.
Cooks tip: You can make the fish pie ahead, ready to bake. After assembly, cool, cover with clear film and refrigerate until required. Add an extra 5-10 minutes onto the baking time to allow the centre of the pie to heat after refrigeration. If Taste the Difference Mashing potatoes are not available you can also use Maris Piper potatoes which are great all-rounders.
*All information included in this recipe has been provided by Greenvale.