Bring a large pot of salted water to a rolling boil. Cook the lasagna noodles according to the package directions, usually around 8-10 minutes, until al dente. Once cooked, carefully drain the noodles in a colander and let them cool slightly.

In a Dutch oven, heat over medium heat and add the bulk Italian sausage and ground beef. Brown the meat with the chopped onions for 8-10 minutes until the meat is no longer pink and the onions are translucent. Stir in minced garlic and cook for an additional minute, then drain any excess fat.

Add crushed tomatoes, tomato paste, water, sugar, fresh parsley, dried basil, fennel seed (if using), and season with salt and coarsely ground pepper to the meat mixture. Stir well, bringing the mixture to a gentle boil. Once boiling, reduce the heat and let the sauce simmer uncovered for about 30 minutes.

In a medium bowl, whisk together the large egg, ricotta cheese, remaining parsley, and a pinch of salt until smooth and well combined.

In an ungreased 13x9-inch baking dish, spread approximately 2 cups of the meat sauce evenly across the bottom. Layer three cooked noodles on top, followed by one-third of the ricotta mixture. Sprinkle a layer of shredded mozzarella and grated Parmesan cheese, repeating this layering process until all ingredients are used.

Preheat your oven to 375°F (190°C). Cover the assembled lasagna with aluminum foil and bake for 25 minutes. After this initial bake, remove the foil and continue baking for an additional 25 minutes until the cheese is bubbling and golden brown. Let the lasagna rest for 15 minutes before slicing.