For the sauce
1 tablespoon olive oil
1 cup chopped onion
3/4 cup finely chopped peeled carrots
2 tablespoons minced garlic
8 ounces lean ground beef
6 ounces spicy Italian sausages, casings removed
1 (28-ounce) can crushed tomatoes with added puree
1/4 cup tomato paste
1/4 cup chopped fresh basil
1 tablespoon golden brown sugar
1 tablespoon dried oregano
1 bay leaf
1/2 teaspoon dried crushed red pepper
For the lasagna
15 lasagna noodles (about 12 ounces)
2 (15-ounce) containers part-skim ricotta cheese
1 cup grated Parmesan cheese (about 3 ounces)
1 (10-ounce) package frozen chopped spinach, thawed, drained, squeezed dry
2 large eggs
4 3/4 cups grated mozzarella cheese (about 1 1/4 pounds)
Make the sauce: Heat oil in heavy large saucepan over medium heat. Add onion, carrots and garlic; saute until softened, about 12 minutes. Add beef and sausages to pan; saute until cooked through, breaking up meat with back of spoon, about 5 minutes. Add remaining ingredients. Cover and simmer until flavors blend and sauce measures about 5 cups, stirring occasionally, about 15 minutes. Discard bay leaf. Cool.
Make the lasagna: Preheat oven to 350 degrees. Cook noodles in large pot of boiling salted water until almost tender, about 7 minutes. Drain; cover with cold water.
Combine ricotta and 3/4 cup Parmesan cheese in medium bowl. Mix in spinach. Season to taste with salt and pepper. Mix in eggs.
Drain pasta and pat dry. Spread 1/2 cup sauce over bottom of 13x9-inch glass baking dish. Place 5 noodles over sauce, overlapping to fit. Spread half of ricotta-spinach mixture evenly over noodles. Sprinkle 2 cups mozzarella cheese evenly over ricotta-spinach mixture. Spoon 1 1/2 cups sauce over cheese, spreading with spatula to cover (sauce will be thick). Repeat layering with 5 noodles, remaining ricotta-spinach mixture, 2 cups mozzarella and 1 1/2 cups sauce. Arrange remaining 5 noodles over sauce. Spread remaining sauce over noodles. Sprinkle remaining 3/4 cup mozzarella cheese and 1/4 cup Parmesan cheese evenly over lasagna. (Can be prepared up to 1 day ahead. Cover tightly with plastic wrap and refrigerate.) Cover baking dish with aluminum foil. Bake lasagna 40 minutes; uncover and bake until hot and bubbly, about 40 minutes. Let lasagna stand 15 minutes before serving.