Place a large pot or Dutch oven over medium-high heat. Add the Italian sausage and cook until fully done and lightly browned, breaking the meat into smaller pieces with a spoon as it cooks. Drain away any excess rendered fat.

Add the chopped yellow onion to the sausage and continue cooking for approximately 4–5 minutes, or until the onion has softened. Stir in the freshly minced garlic and cook for 1 additional minute, just until aromatic.

Pour the crushed tomatoes, beef stock, and water into the pot. Stir thoroughly so the liquids combine evenly with the sausage, onion, and garlic.

Mix in the Italian seasoning and bring the soup to a rolling boil. Add the broken lasagna sheets, stirring from time to time to keep the pasta pieces from sticking together.

Lower the heat and maintain a gentle simmer for about 15 minutes, or until the lasagna pieces are tender and completely cooked.

Once the pasta has reached the desired tenderness, stir the freshly torn basil into the soup. Taste and season with salt and pepper as necessary.

Keep the soup warm until serving so the ingredients remain well combined and heated throughout.

Prepare the ricotta, grated Parmigiano-Reggiano, and shredded mozzarella immediately before serving.

Ladle the hot lasagna soup into individual bowls. Top each portion with dollops of room-temperature ricotta, a generous scattering of Parmigiano-Reggiano, and shredded mozzarella. Allow the heat of the soup to gently soften the cheeses before serving.