Mushroom Moussaka

1. Preheat the oven to hot 220°C (425°F/Gas 7). Line a large baking tray with foil and brush with oil. Put the eggplant and potato in a single layer on the tray and sprinkle with salt and pepper. Bake for 20 minutes.

2. Meanwhile, melt the butter in a large frying pan over medium heat. Add the onion and cook, stirring, for 3-4 minutes, or until soft. Add the garlic and cook for 1 minute, or until fragrant. Increase the heat to high, add the mushrooms and stir continuously for 2-3 minutes, or until soft. Add the tomato, reduce the heat and simmer rapidly for 8 minutes, or until reduced. Stir in the sugar.

3. Melt the extra butter in a large saucepan over low heat. Add the flour and cook for 1 minute, or until pale and foaming. Remove from the heat and gradually stir in the milk. Return to the heat and stir constantly until it boils and thickens. Reduce the heat and simmer for 2 minutes. Remove from the heat and, when the bubbles subside, stir in the egg and Parmesan.

4. Reduce the oven to moderate 180°C (350°F/Gas 4). Grease a shallow 1.5 litre ovenproof dish. Spoon one third of the mushroom mixture into the base of the dish. Cover with potato and top with half the remaining mushrooms, then the eggplant. Finish with the remaining mushrooms, pour on the sauce and smooth the top. Bake for 30-35 minutes, or until the edges bubble. Leave for 10 minutes before serving.