Prepare the Meat Sauce:
In a large pan, heat olive oil over medium heat. Add chopped onion and minced garlic, sautéing until soft. Then, add the ground beef and cook until browned, draining any excess fat. Stir in the tomato paste, crushed tomatoes, oregano, basil, salt, pepper, and sugar. If using, pour in the red wine or beef broth and let the mixture simmer for 20-30 minutes, until it has thickened.
Prepare the Bé Chamel Sauce:
In a separate saucepan, melt the butter over medium heat. Whisk in the flour for 1-2 minutes until smooth. Gradually pour in the warm milk while whisking continuously to prevent lumps. Add salt and nutmeg, cooking until the sauce thickens. Finally, remove from heat and stir in grated Parmesan cheese.
Assemble the Lasagna:
Preheat your oven to 375°F (190°C). Begin by spreading a thin layer of meat sauce at the bottom of a baking dish. Then, add a layer of lasagna noodles, followed by more meat sauce, béchamel sauce, and a generous sprinkle of shredded mozzarella. Repeat the layers until all ingredients are used, finishing with béchamel sauce and the remaining Parmesan cheese on top.
Bake & Serve:
Cover the lasagna with aluminum foil and bake for 30 minutes. Afterward, remove the foil and bake for an additional 15 minutes until the surface is golden and bubbly. Once baked, let it rest for about 10 minutes before slicing. Garnish with fresh basil and serve warm!