
In a medium Dutch oven, heat the olive oil over medium heat. Add the onion, carrot, and celery, and cook, stirring frequently, until the vegetables start to soften, 5 to 7 minutes. Add the garlic, salt, pepper, Italian seasoning, and red pepper flakes, cooking until fragrant, 1 minute.
Stir in the chicken broth and bring to a boil. Add the chicken and tortellini and simmer until the chicken is warmed through and the tortellini is tender, 3 to 5 minutes. Sprinkle with the fresh parsley and serve hot with grated parmesan cheese.