In a skillet or crockpot bowl if available over medium high heat, brown the sausage. Once cooked, drain any excess fat and transfer the meat to the crockpot.
Add the onions and saute for 3 minutes.
Add the garlic and cook for 30 secs to 1 minute.
To the crockpot, add the diced onion, minced garlic, crushed tomatoes, diced tomatoes, vegetable broth, Italian seasoning, salt, and pepper. Stir to combine all the ingredients.
Cover the crockpot and cook the soup on low for 6-8 hours or on high for 3-4 hours. This allows the flavors to meld and the ingredients to cook to perfection.
About 30 minutes before serving, add the sliced zucchini and spinach
Once zucchini is soft add cheese and stir until melted.
Ladle the lasagna soup into bowls and garnish with chopped fresh basil leaves and shaved parmesan cheese.