The Eggplants

1. Cut the eggplants into 1 cm slices.
2. Lay them on a parchment-lined baking tray, drizzle with olive oil, and season with salt and pepper.
3. Bake at 180 °C (350 °F) for about 30 minutes, until soft and lightly browned.

The Meat Sauce

1. Heat a pot over high heat.
2. Add the ground beef and cook until well browned, breaking it up with a spoon.
3. Lower the heat, add the olive oil and onion, and sauté for about 5 minutes, until softened.
4. Add the wine (if using) and cook 2 minutes, until the alcohol evaporates.
5. Stir in the tomato paste, chopped tomato, spices, sugar, salt, and pepper.
6. Simmer gently for 30 minutes, until most of the liquid has evaporated.
7. Remove from the heat and let cool slightly.

The Béchamel Sauce

1. Melt the butter in a saucepan over medium heat.
2. Stir in the flour and cook, whisking constantly, for about 5 minutes.
3. Add the milk – all at once – while whisking to keep it smooth.
4. Continue stirring for another 5 minutes, until thick and creamy.
5. Remove from the heat, add nutmeg, salt, and pepper.
6. If using egg yolks, whisk them in slowly so they don’t scramble.
7. If not using immediately, cover with cling film touching the surface.

Assemble

1. Preheat the oven to 180 °C (350 °F).
2. Grease a deep baking dish with butter or olive oil and layer half the eggplants on the bottom, slightly overlapping.
3. Spread the meat sauce evenly on top, then layer the remaining eggplants.
4. Pour the béchamel sauce over the top and spread evenly.
5. Sprinkle generously with grated cheese.
6. Bake for 40 minutes, until the top is golden and bubbling.
7. Remove from the oven and let rest for at least 15 minutes before serving.