In a large pot, heat the olive oil over medium heat. Add the diced onion and sauté until softened, about 3-4 minutes.
Add the minced garlic, sliced carrots, and celery to the pot; cook for another 5 minutes until the vegetables start to soften.
Crumble the Italian sausage into the pot, cooking until browned and fully cooked through, about 6-8 minutes. Stir occasionally and break up the sausage with a spoon.
Pour in the vegetable or chicken broth and add the diced tomatoes (with their juices) and Italian seasoning. Bring the mixture to a gentle boil.
Add the cheese tortellini and cook according to package instructions, usually about 3-5 minutes until they float to the top and are tender.
Stir in the chopped kale (or spinach) and cook for an additional 2 minutes until wilted.
Season the soup with salt and pepper to taste, adjusting seasoning as necessary.
Ladle the soup into bowls and garnish with fresh parsley and a sprinkle of grated Parmesan cheese on top.
Notes
Feel free to substitute kale with spinach if preferred.