Heat 1 tbsp olive oil in a large pan or pot over medium heat. Add the onion and fry until soft and golden, then add in the garlic and fry for a minute longer. Add in the beef and fry until completely browned, breaking it up as you go. Stir in the tomato paste and fry for a couple of minutes, then pour in the wine. Deglaze the pan if needed, then pour in the passata and beef stock. Add in the parsley, thyme, cinnamon, salt, sugar, pepper, and bay leaf. Stir and simmer for around 30 minutes until thick.

Rest a few sheets of paper towel on a flat surface and lay on the eggplant slices. Rub a pinch of salt over both sides and add two layers of paper towels on top. Add the zucchini slices, followed by another layer of paper towel. Finish with the potato slices and another layer of paper towel on top. Press down to soak up moisture from all layers.

Heat oil in a suitably sized pan until it gently sizzles (aiming for around 150C/300F). Fry the potato slices until lightly golden and fork-tender. Remove and drain on fresh paper towels. Increase the oil temperature to around 170C/340F and fry the zucchini until softened and lightly browned, then finish with the eggplant slices. Drain again on paper towels.

Melt the butter in a pot over medium heat. Stir in the flour to create a roux, gradually pour in the milk while whisking to avoid lumps. Once thick, stir in the salt, white pepper, and nutmeg. If still thin, simmer longer until thick. Stir in the pecorino until lump-free, then whisk in the egg yolks. Take 1/2 cup of the sauce and stir it into the beef.

In a baking dish, add a layer of potato, sprinkle with parsley, pecorino, salt, and pepper. Follow with zucchini, then half of the eggplant with a pinch of salt and pepper. Spread over the beef layer, top with the rest of the eggplant, and then top with the Béchamel sauce.

Sprinkle with pecorino and bake in the oven at 180C/350F for 35-45 minutes until golden. Let sit for at least 15 minutes before serving.