Prepare the Meat Sauce: In a large skillet, brown the ground beef and pork over medium heat until cooked through. Drain excess fat. Add the chopped onion and minced garlic, cooking until softened. Stir in crushed tomatoes, tomato paste, oregano, and basil. Season with salt and pepper to taste. Let the sauce simmer for 15-20 minutes.
Make the White Sauce (Béchamel): In a saucepan, melt butter over medium heat. Whisk in flour and cook for 2 minutes, then slowly add the milk, whisking continuously until the sauce thickens (about 5-7 minutes). Season with salt and pepper, then remove from heat.
Assemble the Lasagna: Preheat the oven to 375°F (190°C). Spread a thin layer of meat sauce at the bottom of a 9x13-inch baking dish. Layer lasagna noodles on top, followed by white sauce, ricotta cheese, mozzarella, and Parmesan. Repeat the layers until the dish is full, finishing with a layer of cheese on top. Cover with aluminum foil.
Bake the Lasagna: Bake for 25 minutes, then remove the foil and bake for an additional 10 minutes to brown the cheese. Let the lasagna rest for 10 minutes before serving to help it set.
