Roast potato fish pie

Heat the oven to 220C/200C fan/gas 7. Drizzle the oil over a large baking tray and slide into the oven to heat up. Tip the potatoes into a large pan, cover with water and season with salt. Bring to the boil, then reduce the heat and simmer for 8-10 mins. Drain and leave to steam-dry.

Carefully remove the baking tray from the oven and tip in the potatoes. Sprinkle with sea salt and black pepper and turn to coat in the oil. Roast for 35-40 mins until crisp, turning halfway through.

Meanwhile, make the filling. Melt the butter in a large saucepan over a medium heat and cook the shallots for 5 mins until softened. Pour in the wine and simmer for 2 mins until it has reduced. Sprinkle in the flour and stir until you have a paste.

Gradually whisk in the milk until you have a smooth sauce, then stir in the mustard and cream. Simmer for 2 mins, whisking occasionally. Tip in 100g of the cheese, the peas and fish pie mix, cover and cook for 8 mins more, stirring occasionally until the peas have defrosted and the fish is almost cooked through. Stir in the parsley and lemon zest and juice, then season to taste.

Pour the filling into a deep 20 x 25cm casserole dish and scatter the roasted potatoes over the top. Sprinkle with the remaining cheese. Turn down the oven to 200C/180C fan/gas 6 and bake the pie for 15-20 mins until the filling is bubbling at the edges. Serve with winter greens or a crisp salad.