Creamy Fish And Mushroom Pie - cooking recipe

Ingredients

225 g assorted mushrooms, such as oyster, horse, shiitake, trimmed and quartered
675 g cod or 675 g haddock fillets, skinned and diced
600 ml milk, low-fat is fine, boiling
For the Topping
900 g floury potatoes, peeled and quartered
25 g unsalted butter
150 ml milk, low-fat is fine
salt, to taste
fresh ground black pepper, to taste
grated nutmeg, to taste
For the Sauce
50 g unsalted butter
1 medium onion, chopped
1/2 celery rib, chopped
50 g plain flour
10 ml lemon juice
2 tablespoons fresh parsley, chopped

Preparation

Preheat the oven to 200\u00b0C/400\u00b0F/Gas 6 and butter an ovenproof dish, scatter the mushrooms in the bottom, add the fish and season with salt and pepper, to taste; pour the boiling milk over the top, cover and cook in the oven for 20 minutes.
While the mushrooms and fish are cooking, cover the potatoes with cold water; add a good pinch of salt and boil for 20 minutes; drain and mash with the butter and milk, and season to taste.
Using a slotted spoon, transfer the fish and mushrooms to a 1.5 litre (11/2 quart American; 1.5 litre Canadian) baking dish. Pour the poaching liquid into a jug and set aside.
To make the sauce: Melt the butter in a saucepan, add the onion and celery and saute until soft but not browned; stir in the flour, then remove the pan from the heat; slowly add the reserved liquid to the pan, stirring until it has been absorbed; then return the pan to the heat, stir and simmer to until the sauce thickens; add the lemon juice and parsley, season to taste, then add the sauce to the baking dish, using the sauce to cover the fish and the mushrooms.
Top with the mashed potato and place the baking dish in the oven for 30-40 minutes until the potatoes are golden brown.