Step 1: In a large stockpot, add onion, garlic, oregano, mushrooms, bell pepper, and red pepper flakes and a bit of olive oil (if needed) and saute about 5 minutes. Then, add in sausage and tomato paste and saute until lightly browned.
Step 2: Add in the tomaotes, broth and bay leaf.
Step 3: Simmer the soup for 30 minutes to allow the flavors to blend.
Step 4: Add in the pasta and spinach and cook until tender; about 7-9 minutes. Remove the bay leaf. Add in basil and season with salt and pepper.
Step 5: Place ricotta cheese in the bottom of the soup bowl.
Step 6: Top with Parmesan cheese, mozzarella cheese, salt and pepper, as desired.
Step 7: Serve soup over the cheeses in the bowl.