Breadcrumbs for bottom of casserole dish (optional)
For the béchamel sauce:
100g unsalted butter
100g plain flour
900ml whole milk
Pinch of salt and pepper
½ tsp ground nutmeg
100g grated Parmesan cheese
2 egg yolks
Place the sliced aubergines on kitchen paper, sprinkle with salt, and leave for 30 minutes to draw out the moisture, then rinse in a colander and pat dry with kitchen paper, then sprinkle with a little flour.
Place a little oil in a frying pan and fry the aubergine slices in batches, for a few minutes each side, to colour. Place on kitchen paper.
Place the potato slices in a pan of boiling water for 5 minutes, drain, and rinse with cold water to prevent further cooking.
Preheat the oven to 180˚C / 160˚C fan / Gas 4.
Make the mince mixture by frying the lamb mince until browned, add the onions and garlic and cook for a few minutes to allow the onions to soften. Add the tomatoes, purée, cinnamon, oregano, seasoning, bay leaves and the wine. Bring to the boil, and then simmer for approximately 30 minutes until it reaches a thick consistency. Allow to cool slightly.
Make the béchamel sauce by melting the butter in a saucepan, then add the flour and whisk for 2 minutes. Gradually whisk in the milk until the sauce is nice and smooth. Bring to the boil, and then take off the heat and add the cheese, nutmeg and seasoning. Whisk again until nice and smooth. Allow the sauce to cool for approximately 15 minutes, then whisk in the egg yolks.
Grease a baking dish or roasting tin, and then add a thin layer of breadcrumbs to absorb the liquid from the vegetables. Place the potato slices on the bottom, overlapping them slightly. Then place a layer of the aubergine slices on top, overlapping them. Spoon over the meat mixture, then another layer of the aubergines. To finish, pour over the béchamel sauce.
Place in the oven for approximately 1 hour. It is best to let it stand for 10-15 minutes before serving.