Put the chopped onion and extra virgin olive oil in a frying pan and cook until the onion is soft and almost transparent.
Add the mince and break any lumps with a wooden spoon. Cook over medium–high heat until the meat browns well.
Add the tomato purée, salt, pepper, parsley, bay leaf, mixed herbs, and cinnamon. Stir, add a glass of water, cover, and cook on low heat until the sauce thickens.
When the mince is brown, add the wine, increase the heat, and let the alcohol evaporate.
When the sauce is ready, set it aside.
For the Vegetables
Slice the eggplants and zucchini into 1 cm slices and the potatoes into ½ cm slices.
Place the sliced eggplants in salted cold water for at least half an hour to reduce bitterness.
Deep-fry all the vegetables in hot vegetable oil in batches and place them on kitchen paper to drain any excess oil.
For the Cheese Sauce
Heat the milk and set it aside. Melt the butter in a medium pot.
Add the flour and stir with a wooden spoon or whisk until smooth and lump-free.
Slowly pour in the hot milk while stirring continuously. Add salt and cook the sauce for 5 minutes.
Add the grated Pecorino Romano and stir. Turn off the heat, cover the pot to prevent a skin from forming, and let the sauce cool.
Lightly beat the eggs and add them to the cooled sauce. Stir well and set aside.
Assembling the Moussaka
Place a layer of eggplants in an ovenproof dish, followed by a layer of meat sauce.
Add a layer of potatoes, then another layer of meat sauce.
Add the zucchini, another layer of meat sauce, and finish with eggplant and meat sauce.
Pour the cheese sauce evenly over the top.
Bake in a preheated fan-forced oven at 180°C – 355°F for 20 minutes or until golden and heated through.