Fish pie with a rosti topping recipe by Rosie Sykes

Fish pie is a firm family favourite – this one cuts out a lot of the work, such as making a white sauce and mashed potato.

Serves 4
firm white fish fillets 500g
leek 1, finely sliced, using as much of the green part as possible
hot milk 300ml
cream cheese with herbs and garlic 100g
baby spinach 100g
parsley a small handful, chopped
tarragon a few sprigs, leaves chopped (optional)
smoked mackerel 80g, flaked
potted shrimps 1 tub (about 55g)
lemon grated zest and juice of ½
large red-skinned potatoes 700g, peeled
capers 2 tbsp
butter 60g, melted
sea salt and black pepper

Preheat the oven to 200C fan/gas mark 7. Put the white fish, leek and milk into a small roasting pan, season well and cover with foil. Bake for 15 minutes until the fish is cooked and the leek has softened.

Strain off the milk into a food processor and add the cream cheese, spinach and herbs. Whizz to make a smooth, thickish sauce.

Separate the fish from the leeks, remove the skin if there is any, and flake the fish. Mix together the poached fish, mackerel and leeks. Break up the potted shrimps as best you can and add them, too. Add the lemon juice and zest and stir in the herby sauce. Taste and adjust the seasoning. Spread this mixture evenly in the roasting pan.

Coarsely grate the potatoes and toss with the capers, melted butter and plenty of seasoning. Spread the potato mix evenly over the fish.

Bake for 35 minutes until the topping is golden and crisp on top and fluffy underneath. Test by piercing the potato topping with a sharp knife: it should slide through easily. Leave to stand for 5 minutes before serving. I like to have fish pie with peas.

From Roasting Pan Suppers by Rosie Sykes and National Trust Books (HarperCollins, £14.99)