Sustainable fish pie

Put the milk, onion, cloves, bay leaves and peppercorns in a medium-sized pan, then slowly bring to the boil. Carefully add the fish into the hot milk, reduce the heat and poach for 6-8 mins, adding the prawns for the final 3 mins. Using a slotted spoon, lift the fish into a medium-sized ovenproof dish, strain the milk and set aside.

Melt the butter in a saucepan, then add the flour and cook, stirring constantly, for 1 min. Gradually stir in the milk on a low heat so that it's fully incorporated into the sauce, then gently simmer for 5-10 mins until thickened. Finally, add the parsley, a pinch of nutmeg and some seasoning. Pour the sauce over the fish, then set aside.

To make the mash, boil the potatoes until cooked, then drain well. Place the pan over the heat again, add the milk and butter, and mash until smooth. Season with salt, pepper and nutmeg.

Heat oven to 200C/180C fan/gas 6. Spoon the mash onto the fish mixture, spread out evenly, then rough up slightly with a spoon or a fork. Dot the pie with butter, then place in the oven for 35-40 mins until piping hot and golden on top. If you want it to be extra crisp on top, flash the pie under a hot grill at the end to get it nice and brown.