Cooking Sausage: In your soup pot, warm up the olive oil over medium heat. Crumble the sausage into the pot, cooking until it's well-browned, which takes about 3-5 minutes. Remember to stir and break it apart. After browning, remove any extra fat.
Adding Aromatics: Mix in the garlic, onion, and Italian seasoning with the sausage. Stir them together until the onion is clear and soft, about 2-3 minutes. Add salt and pepper according to your preference.
Thickening the Soup: Sprinkle flour over the mixture, stirring for a minute until it turns a slight brown. This helps thicken your soup.
Creating the Broth: Slowly add in the chicken stock and tomato sauce while whisking to avoid lumps. Bring it to a boil, then reduce to a simmer. Let it cook for 10 minutes, stirring now and then, until it thickens a bit.
Adding Tortellini: Put in the tortellini, cover the pot, and let them simmer until they are tender, about 5-7 minutes.
Finishing Touches: Add the kale, stirring until it wilts, approximately 1-2 minutes. Pour in the heavy cream and basil, warming it through for a minute. Do a final taste test and adjust salt and pepper as needed.
Ready to Serve: Your Tortellini Soup is now ready to be enjoyed. Serve it hot for a cozy, comforting meal.