Brown the Sausage. In a skillet, brown the ground Italian sausage over medium heat. Once browned, drain any excess fat and transfer the sausage to your slow cooker.
Add Ingredients to the Slow Cooker. Add crushed tomatoes, tomato sauce, broth, chopped onion, minced garlic, Italian seasoning, salt, and pepper to the slow cooker. Stir everything to combine.
Cook Low and Slow. Set your slow cooker to low and cook for 6-7 hours, or on high for 3-4 hours, until the flavors have melded and the onions are tender.
Add the Lasagna Noodles. About 30 minutes before serving, break the lasagna noodles into bite-sized pieces and add them to the slow cooker. Stir to ensure they’re submerged in the liquid. Cook until the noodles are tender.
Add Cheese. Stir in ricotta cheese and top the soup with mozzarella cheese. Let the mozzarella melt into the soup for an extra cheesy finish.
Serve & Garnish. Ladle the soup into bowls, and garnish with fresh basil, if desired. Serve with crusty bread for a complete meal!