In a spacious Dutch oven, warm over medium heat and add the sweet Italian sausage and lean ground beef. Cook for about 5–7 minutes, breaking up the meat with a wooden spoon until browned and no longer pink. Stir in minced onion and crushed garlic, allowing them to sauté for another 2–3 minutes until fragrant and translucent.

Once the meat is cooked, add crushed tomatoes, tomato paste, and canned tomato sauce to the pot. Mix in sugar, dried basil, fennel seeds, Italian seasoning, salt, and pepper. Bring the mixture to a gentle simmer, reducing the heat slightly. Let the sauce cook uncovered for about 1.5 hours, stirring occasionally until thickened and flavorful.

In a separate mixing bowl, combine ricotta cheese with the egg, chopped fresh parsley, and a pinch of salt. Use a spatula to blend thoroughly until smooth and creamy.

As the sauce simmers, preheat your oven to 375°F (190°C). This will ensure that your lasagna cooks evenly.

In a 9x13-inch baking dish, spread 1.5 cups of the meat sauce to form the first layer. Lay down 3–4 noodles, then spread half of the ricotta mixture over the noodles. Sprinkle a third of the sliced mozzarella on top, followed by another 1.5 cups of meat sauce. Repeat the layering process until all ingredients are used, finishing with remaining mozzarella and grated Parmesan.

Cover the lasagna with aluminum foil and bake in the preheated oven for 25 minutes. After 25 minutes, remove the foil and continue baking for an additional 25 minutes until the top is bubbling and golden brown.

Once baked, remove the lasagna from the oven and let it rest for about 10 minutes. This cooling period allows the layers to set.