Add olive oil to a heavy large pot over medium heat, add the diced onions and sweat for 8-10 minutes with a pinch of salt.
Add minced garlic and mix through for a minute.
Increase heat to high, add beef mince, break it into pieces, and brown it.
Add oregano, paprika, cinnamon, and cook for a minute.
Pour in red wine, cook out half the liquid, then add crushed tomatoes and bay leaves. Season to taste.
Simmer for 60-90 minutes until most liquid is gone.
Preheat oven to 180°C.
Slice eggplant and potatoes, season with salt, and roast them in olive oil.
For the béchamel sauce, whisk olive oil and flour in a pot over high heat. Add milk, whisk until thickened. Remove from heat, whisk in eggs, yolks, nutmeg, cheese, and salt.
Layer potatoes, eggplant, ragu, and béchamel sauce in a baking dish. Bake at 180°C for 40-45 minutes.
If needed, grill for a few minutes for color. Let it rest for at least 30 minutes before serving.
