2. Arrange eggplant slices on a baking sheet, brush with olive oil, and bake for 20 minutes until tender.
3. In a skillet, cook ground beef, onion, and garlic until beef is browned. Add tomato sauce, cinnamon, oregano, salt, and pepper. Simmer for 15 minutes.
4. For the béchamel sauce, melt butter in a saucepan, stir in flour, and cook for 2 minutes. Gradually whisk in milk, cook until thickened. Stir in nutmeg and Parmesan. Remove from heat and stir in egg yolks.
5. In a baking dish, layer half of the eggplant slices, all of the meat sauce, remaining eggplant slices, and top with béchamel sauce.
6. Bake for 30-35 minutes until top is golden and bubbly. Let cool for 10 minutes before serving.
Notes:
For a vegetarian version, replace ground beef with lentils or a meat substitute.