Heat olive oil in a large soup pot or Dutch oven over medium-high heat. Add the chicken, half of the Italian seasoning, salt, and pepper. Cook for 4–5 minutes until lightly browned on all sides.
Add the onion, carrots, celery, sun-dried tomatoes, and garlic to the pot. Cook for 3–4 minutes, stirring, until vegetables begin to soften.
Sprinkle in the flour gradually, stirring constantly to coat the ingredients evenly. If using tomato paste, stir it in at this stage.
Slowly pour in the chicken broth while stirring to prevent lumps, scraping the bottom of the pot to release any browned bits.
Bring the soup to a gentle boil, then add the pasta, remaining Italian seasoning, salt, and pepper. Cover, reduce heat to low, and simmer for about 20 minutes, or until the pasta is tender and the chicken is fully cooked.
Stir in the heavy cream, spinach, and Parmesan cheese. Simmer uncovered for another 5 minutes, until the spinach wilts and the soup becomes creamy.
Taste and adjust seasoning as needed. Serve warm.
