Heat olive oil in a large pot or Dutch oven over medium heat. Add the Italian sausage and cook, breaking it up with a spoon, until browned. Drain off excess grease.
Add the chopped onion, carrots, and celery to the pot. Cook until the vegetables soften, about 5 to 7 minutes.
Stir in the minced garlic and cook for 1 minute until fragrant.
Pour in the chicken broth and add the diced tomatoes (with juice), Italian seasoning, oregano, and red pepper flakes if using. Bring the mixture to a simmer.
Reduce heat to medium-low, cover, and cook for 10 minutes to allow the vegetables to tenderize slightly.
Add the cubed cream cheese to the pot. Stir constantly until the cream cheese melts completely into the broth, creating a creamy base.
Add the refrigerated tortellini to the soup. Cook according to package directions, usually about 5 to 7 minutes, until the tortellini float and are cooked through.
Stir in the fresh spinach until it wilts into the soup, which takes about 2 minutes.
Remove the pot from the heat. Stir in the heavy cream. Season with salt and pepper to your taste.
Serve immediately, topped with grated Parmesan cheese.
Notes
For a thicker soup, use only 5 cups of chicken broth initially.
You can substitute kale for spinach; add kale earlier with the broth to give it more time to soften.
This recipe works well for meal prep; store leftovers in airtight containers in the refrigerator for up to 3 days.