Pat the chicken breasts dry, then season both sides with salt, black pepper, and Italian seasoning.
Heat the olive oil in a large skillet over medium heat.
Add the chicken breasts and cook for 5 to 7 minutes per side, or until golden brown and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the garlic and cook for about 30 seconds until fragrant.
Pour in the chicken broth and stir, scraping up any browned bits from the bottom of the pan.
Add the heavy cream and Parmesan cheese, then stir until the sauce becomes smooth and creamy.
Mix in the chopped sun-dried tomatoes and fresh spinach. Cook until the spinach wilts.
Return the chicken to the skillet and spoon the sauce over the top.
Simmer for 2 to 3 minutes so the flavors come together.
Stir in the butter if you want an even richer finish.
Garnish with fresh parsley if desired, then serve warm.