Remove the stalks from the eggplants and cut them into slices, 1 cm thick. Season with salt and place in a colander for about half an hour.

Rinse the eggplants with plenty of water and squeeze with your hands, to get rid of the excessive water. Pat them dry and fry in plenty of oil until nicely colored. Place the fried eggplants on some paper to absorb the oil.

Slice the potatoes into 0.5cm slices. Fry or bake them in the same way as the eggplants, seasoning with some salt.

Heat a large pan to medium-high heat and add the olive oil. Stir in the chopped onions and sauté until softened and slightly colored. Stir in the mince breaking it up and sauté until it starts to brown.

Add the garlic and tomato paste, sauté until the garlic starts to soften. Pour in the red wine to deglaze and let it evaporate.

Add the tinned tomatoes, sugar, a pinch of cinnamon, bay leaf, cloves, and salt and pepper. Bring to the boil, then turn down heat and simmer with the lid on for about 30 minutes or until most juices have evaporated.

Melt the butter in a large pan over low-medium heat. Add the flour, whisking continuously to make a paste. Gradually add warmed milk, whisking to prevent lumps.

If the sauce needs to thicken, boil over low heat while stirring until it resembles a thick cream. Remove from stove and stir in egg yolks, salt, pepper, nutmeg, and most of the grated cheese. Reserve some for topping.

Butter the bottom and sides of a baking dish. Layer the potatoes first (if using), then half the eggplants. Pour in all of the meat sauce and spread evenly. Add a second layer of eggplants, then top with all of the béchamel sauce.

Sprinkle with the remaining grated cheese. Preheat oven to 180C/350F and bake for about 60 minutes or until crust is light golden brown. Let cool slightly before serving.