Salt both the eggplant & zucchini slices and let sit 15 minutes. Blot dry with a paper towel. Place each vegetable in a single layer on a parchment lined baking sheet. Drizzle with olive oil and sprinkle with salt and pepper. Bake at 350, the eggplant and zucchini for about 20 minutes and the potatoes for about 25 minutes, depending on how thinly they are sliced.
Brown Beef. Remove from the pan and drain. In the fat remaining, add onions and cook for 3-4 minutes. Add the garlic, tomato paste & thyme. Cook for an additional 1-2 minutes, then deglaze the pan with red wine, scraping up any of the cooked bits off the bottom of the pan. Pour in beef stock, honey, bay leaf and passatta/tomato sauce. Let simmer for 5-7 minutes. Add the beef back into the pan and let simmer an additional 5-7 minutes. Stir in parsley.
Melt your butter and add the flour, season and stir continuously. After about 2 minutes, slowly drizzle in the milk. Continue to whisk until thickened. Remove from heat and add in Parmesan, egg yolks & nutmeg. Stir until smooth.
To assemble begin by adding your layer of potatoes, then sprinkle cheese and parsley. Proceed the same way with the eggplant and zucchini. Next, evenly spread the meat sauce and finally the bechamel. Sprinkle the rest of the parmesan and parsley over the top.
Bake for 35 minutes, then let it rest for 15 minutes before serving. Enjoy!