Instructions

1. Grease the baking dish with butter. Melt 50g (13⁄4oz) 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.
2. Pour the fish mixture into the buttered baking dish and set aside to cool. You can prepare up to this point 1 day ahead and refrigerate over night
3. Melt the remaining butter in a large, non-stick, deep-sided frying pan or sauté pan over a medium heat. Add the spinach and cook, stirring, for 11⁄2–2 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 200oC (fan 180oC/400oF/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 p59, 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 p59, 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.