A small bunch of flat leaf parsley, roughly chopped
Salt and freshly ground black pepper
How to make
Preheat the oven to 200°C / 180°C / gas 6
Add the potatoes to a pan and cover with cold water. Shake in a little salt and bring up to the boil. Cook until soft, about 15 minutes then drain well. Mash until smooth, then beat in the butter and season with the nutmeg and a little salt and pepper. Keep warm over a very low heat.
Whilst the potatoes are cooking, make the filling. Lay the fish in a deep frying pan, tuck in the bay leaves and pour over the milk. Dot the surface with about a third of the butter and season with a little salt and freshly ground black pepper. Cover with a lid or tight fitting piece of foil and poach for a few minutes until the fish is cooked all the way through. Set aside until cool enough to handle. Flake with a fork and add to a baking dish and evenly scatter over the prawns. Reserve the poaching milk.
In a clean saucepan melt the rest of the butter, then stir through the flour to form a roux. Allow to cook over a gentle heat for a minute before pouring over the stock and reserved poaching milk, whisking all the time until it thickens. Season to taste with salt and pepper and allow to simmer steadily for 5 minutes. Stir through the parsley and pour the sauce over the seafood, spreading it evenly.
Using a fork, spread the mashed sweet potato over the fish filling and fluff up the top. Sprinkle over the cheese and bake in the oven for around 30 minutes, until the pie is bubbling and the top golden and crisp. Serve with a big dish of peas on the side.