Heat olive oil in a large stockpot or Dutch oven over medium heat.
Add Italian sausage and cook until browned, about 3-5 minutes, crumbling the sausage as it cooks. Drain excess fat if needed.
Stir in garlic, onion, and Italian seasoning. Cook, stirring frequently, until onions are translucent, about 2-3 minutes. Season with salt and pepper to taste.
Whisk in the flour and cook until lightly browned, about 1 minute.
Stir in chicken stock, tomato sauce, and Parmesan rind (if using). Bring to a boil, then reduce heat and let simmer, stirring occasionally, until slightly thickened, about 10 minutes.
Add tortellini, cover, and cook until tender, about 5-7 minutes.
Stir in kale and cook until wilted, about 1-2 minutes.
Stir in heavy cream and basil, cooking for another minute until heated through. Season with additional salt and pepper if needed.
Serve immediately and enjoy!