Season each side of each pounded chicken breast with Italian Seasoning and salt and pepper.
Combine flour and grated parmesan in a shallow bowl. Dredge each chicken breast in the flour mixture, coating both sides.
Heat a large skillet over medium-high heat. Add the 2 tablespoons butter and stir/melt.
Cook the chicken (in batches if necessary) for 4-5 minutes per side or until its fully cooked (165°F in the center and no longer pink) and browned on both sides. Remove from the skillet and place on a plate. Cover with foil.
Return the skillet to medium-high heat, and add the remaining ¼ cup butter. Use a wooden spoon to scrape the bottom of the pan as the butter melts. The brown bits hold a lot of flavor, so no need to remove them.
Add the garlic and sun-dried tomatoes and cook for 1-2 minutes or until fragrant.
Whisk in the flour and allow to thicken for approximately 1 minute.
Whisk in the heavy cream, chicken broth, parmesan cheese, Italian seasoning, and pepper. Stir to combine.
Add the spinach and reduce heat to simmer. Allow to cook until the sauce slightly thickens and the spinach wilts.
Add the chicken back into the skillet and turn to coat in the sauce. Allow to continue to simmer until the chicken is heated through, 2-3 minutes. Garnish with fresh parsley.
