In a large pot over medium heat, add in ground sausage and ground beef. Use a spoon to break up the meat into small pieces. Add in onion and garlic and cook until meat is well browned, stirring constantly. Stir in sugar, fresh basil, fennel, oregano, ½ teaspoon salt, pepper, and ¼ cup chopped parsley. Pour in crushed tomatoes, tomato paste, tomato sauce, and chicken broth. Stir well and bring to a simmer. Reduce heat to low and simmer 1-4 hours, stirring occasionally.
Meanwhile, place lasagna noodles into the bottom of a pan. Pour hot tap water directly over the noodles, making sure the pasta is completely immersed in the water. Let them soak for 30 minutes, then drain and discard water.
In a mixing bowl, combine ricotta cheese with egg, remaining 2 tablespoons parsley, ½ teaspoon salt, and nutmeg. Refrigerate until ready to assemble lasagna.
Preheat oven to 375 degrees. Lightly grease a deep 9x13 pan.
To assemble, spread about 1 cup of meat sauce in the bottom of the prepared pan. Place 4 noodles on top. Spread with ⅓ of the ricotta cheese mixture. Top with ¼ of mozzarella cheese slices. Spoon 1½ cups meat sauce over mozzarella, then sprinkle with ¼ cup parmesan cheese. Repeat layering two more times to create three complete layers. To finish, place a final layer of pasta, topped with another 1 cup of meat sauce to cover the pasta. Top with remaining mozzarella and Parmesan cheese. Cover loosely with aluminum foil.
Bake in preheated oven for 25 minutes. Remove foil, and bake an additional 25 minutes to allow cheese to brown. Serve hot.