1. Heat the olive oil in a large soup pot or Dutch oven over medium-high heat. Add the diced chicken, 1 teaspoon of Italian seasoning, salt, and pepper to taste. Cook until the chicken is browned on all sides, about 4 to 5 minutes.
2. In the same pot, add the onions, carrots, celery, sundried tomatoes, and garlic. Cook until the vegetables become translucent, about 3 to 4 minutes.
3. Sprinkle the flour evenly over the mixture and stir well to combine, adding the flour in stages to prevent drying out. If using tomato paste, add it now and mix thoroughly.
4. Gradually whisk in the chicken broth, stirring continuously to prevent lumps. Deglaze the bottom of the pot with your spoon.
5. Bring the soup to a rolling boil, then add the pasta, remaining 1 teaspoon Italian seasoning, salt, and pepper to taste. Cover the pot, reduce heat to low, and simmer for about 20 minutes until chicken is cooked through and pasta is al dente. Alternatively, cook pasta separately and add at the end.
6. Remove the lid; stir in heavy cream, fresh spinach, and grated Parmesan cheese. Simmer an additional 5 minutes.
7. Taste and adjust seasoning with salt and pepper before serving.