In a large pan, heat oil over medium-high heat. Add sausage and onions. Cook, breaking up sausage, until onions are translucent and sausage is mostly cooked through, 8 to 10 minutes. Add mushrooms and continue to cook, stirring frequently, until browned.
Add spinach and garlic. Cook until spinach is wilted and garlic is fragrant.
Stir in tomato paste until combined. Add tomatoes, oregano, 1 teaspoon parsley, basil, and broth. Bring to a boil, stir in pasta, and reduce to a simmer.
Simmer, stirring frequently, for 10 to 12 minutes or until pasta is al dente. Add more water or broth as needed for desired consistency. Taste and season with salt and pepper as desired.
While the pasta is cooking, mix together ricotta, Parmesan, mozzarella cheese, and remaining 1 teaspoon dried parsley in a small bowl.
To serve, top individual bowls of soup with a spoonful of cheese mixture immediately prior to serving. Garnish with basil, if desired.
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Notes
Whole wheat lasagna noodles can be substituted, if desired.
To keep sodium content lower, use no-salt-added beef broth and no-salt-added canned tomatoes.