Cook bacon in a large pot over medium heat until crisp. Remove bacon with a slotted spoon and set aside.
Add sausage, onion, and garlic to the bacon fat and cook 3-4 minutes or until onion is slightly softened.
Stir in chicken broth, carrot, celery, basil, and chili flakes if using. Simmer for 5 minutes. Add tortellini and simmer 4-5 minutes or until cooked through.
Stir in cream and simmer for 1 more minute. Combine cornstarch and 1 ½ tablespoons water to create a slurry.
Add cornstarch mixture to simmering soup a little at a time while whisking to reach desired thickness, you may not use all of the slurry. Simmer 1 minute.
Remove from heat and add spinach. Taste and season with additional salt and pepper if desired.
Garnish with crumbled bacon, parmesan cheese, and parsley if desired.
