Heat ⅓ cup (100 ml) extra virgin olive oil in a large saucepan over medium heat. Blend 2 yellow onions and 3 garlic cloves into a smooth paste, add them to the pan with 1 teaspoon salt and ½ teaspoon black pepper, and sauté until translucent.
Blend 1 red bell pepper into a paste and add it to the pan. Cook for a few minutes. Blend 2 carrots into a paste, add them, and cook until the vegetables soften.
Add 2.2 lb ground pork (1 kg) with the remaining 1 teaspoon salt and ½ teaspoon black pepper. Cook until the meat is browned, breaking it up with a spoon.
Stir in 3 cups of passata (700 g) and cook for a few minutes. Pour in ½ cup white wine (100 ml), then add 2 bay leaves, 3 cloves, ½ teaspoon thyme, and 1 teaspoon dried oregano. Add ½ cup (100 ml), bring to a simmer, cover, and cook on low heat for at least 1½ hours, stirring occasionally.
Melt ½ cup (125 g) butter in a saucepan over medium heat. Add ½ cup (70 g) wheat flour 00 and whisk over low heat for about 3 minutes until a smooth roux forms. Gradually pour in 4 cups (1 litre) of whole milk while whisking constantly. Season with ¼ teaspoon salt, ⅛ teaspoon black pepper, and ⅛ teaspoon nutmeg, and cook until the sauce thickens.
Spread a thin layer of béchamel on the bottom of a baking dish. Add a layer of 12 oven-ready lasagna sheets, then béchamel, Bolognese, and a sprinkle of 1 cup (100 g) grated Parmesan cheese and 1 cup (100 g) mozzarella cheese. Repeat the layers until everything is used, finishing with béchamel and Parmesan on top.
Cover the baking dish with aluminum foil. Cover with aluminum foil and bake in a preheated oven at 390°F / 200°C (375°F convection / 190°C fan) for 15 minutes. Remove the foil and bake for another 10 minutes until golden and bubbly.
Let the lasagna rest for a few minutes before slicing so the layers set properly.
Notes
Blend the Vegetables Well: I like blending the onion, garlic, red pepper, and carrots into a smooth paste because it helps the sauce cook down evenly and gives it a softer texture.Let the Sauce Simmer Slowly: Cooking the Bolognese gently for about 1½ hours builds deeper flavor in the meat sauce.Whisk the Béchamel Steadily: I keep whisking while adding the milk so the sauce stays smooth and thickens without lumps.Let the Lasagna Rest: Allowing it to sit for a few minutes after baking helps the layers settle and makes slicing easier.