Add the chopped onion it to a large Dutch oven along with the olive oil. Sauté over medium-high heat for 5-7 minutes.
Meanwhile, chop the celery and carrots, then add them to the pot along with the garlic. Give it a good stir and cook for a couple minutes.
Add the chicken broth and seasoning. Increase the heat to high, and once it starts to boil, reduce the heat to a rapid simmer and let it cook for 10 minutes.
Add the chicken, tortellini, and green beans to the pot. Increase the heat to medium and let the soup cook for another 10 minutes or so.
Season with salt & pepper as needed and garnish with the chopped parsley and cheese. Serve immediately.