Heat the olive oil in a large soup pot or Dutch oven over medium-high heat. Add chicken and 1 teaspoon of Italian seasoning and cook until browned. Ensure the chicken pieces are evenly coated and fully cooked to lock in flavor.

In the same pot, add chopped onions, carrots, celery, sundried tomatoes, and garlic, cooking until translucent. The vegetables should be softened and aromatic, forming a fragrant base for the soup.

Sprinkle the flour throughout and stir well to combine, ensuring no lumps remain. This step is crucial for thickening the soup, creating a velvety texture.

Gradually whisk in the chicken broth, stirring repeatedly. This helps in dissolving the flour thoroughly, preventing any clumping.

Bring the mixture to a simmer, adding the remaining 1 teaspoon of Italian seasoning, salt, and pepper to taste. Let the soup simmer for about 20 minutes. The simmering process allows the flavors to meld beautifully.

Stir in heavy cream, spinach, and grated Parmesan cheese, allowing the soup to simmer until the spinach is wilted and the cheese is melted. The creaminess from the cheese and cream adds a luxurious finish to the soup.