Fish pie with crushed potato topping

SERVES 6

75g (2½ oz) butter, plus extra for greasing

1 large leek, trimmed and cut into 5mm (¼ in) thick slices

50g (1¾ oz) plain flour

600ml (1 pint) hot, full-fat milk

1½ tbsp chopped fresh dill finely grated rind of ½ lemon

salt and freshly ground black pepper

400g (14oz) hake fillet, skinned and cut into 2.5cm (1in) cubes (see Buying and using hake, below) 400g (14oz) salmon fillet, skinned and cut into 2.5cm (1in) cubes

200g (7oz) fresh spinach

FOR THE TOPPING

800g (1¾ lb) new potatoes, such as Charlotte, scrubbed

2 tbsp olive oil, plus

2 tsp for drizzling

SPECIAL EQUIPMENT

1.7 litre-2 litre (3 pint-3½ pint) baking dish, about

25cm x 18cm (10in x 7in) and 7.5cm (3in) deep

1 Grease the baking dish with butter. Melt 50g (1¾ oz) of the butter in a large pan over a medium heat. Add the leek and fry for 3 minutes or until softened but not browned. Stir in the flour and cook, stirring, for 1-2 minutes. Remove from the heat and gradually pour in the hot milk. Return to a medium heat and stir until boiling, thickened and smooth. Stir in the dill, lemon rind and some salt and pepper. Add the hake and salmon to the sauce. Cook over a low heat for 2 minutes, stirring gently twice, just to start cooking the fish. (See Keys to Perfection, Make a smooth, creamy filling.)

2 Pour the fish mixture into the buttered baking dish and set aside to cool (see Keys to Perfection, Let the filling cool down). You can prepare up to this point 1 day ahead and refrigerate overnight.

3 Melt the remaining butter in a large, nonstick, deep-sided frying pan or sauté pan over a medium heat. Add the spinach and cook, stirring, for 1½-2 minutes or until it wilts. Drain thoroughly in a colander, pressing down with the back of a wooden spoon to extract excess moisture. Roughly chop and set aside. Preheat the oven to 200C (fan 180C/400F/gas 6).

4 Meanwhile, make the topping: put the potatoes in a large pan of cold salted water and bring to the boil. Cover and simmer for about 15 minutes or until tender. Drain well. Return the potatoes to the pan and, using a fork, break the potatoes down into rough, chunky pieces. (See Keys to Perfection, Make a crispy topping.) Stir in the olive oil and some salt and pepper.

5 Scatter the spinach on top of the cooled fish mixture, then spoon the potatoes over the spinach layer (see Keys to Perfection, Carefully add the topping). Drizzle over the remaining 2 teaspoons of oil and bake for 30-40 minutes or until the pie is bubbling at the edges and the topping is golden and crispy.