Prepare the chicken: Pat the chicken breasts dry with paper towels. Season both sides with Italian seasoning, salt, and black pepper.
Sear the chicken: Heat olive oil in a large skillet over medium-high heat. Add the chicken and cook for about 5–6 minutes per side, or until golden brown and cooked through. Transfer the chicken to a plate and set aside.
Cook the garlic and tomatoes: Reduce the heat to medium. Add the minced garlic and chopped sun-dried tomatoes to the same skillet. Cook for about 1–2 minutes, stirring frequently, until the garlic becomes fragrant.
Add the broth: Pour in the chicken broth and scrape the bottom of the skillet with a wooden spoon to loosen the browned bits.
Make the cream sauce: Pour in the heavy cream and stir well. Bring the mixture to a gentle simmer.
Add Parmesan: Stir in the grated Parmesan cheese and red pepper flakes, if using. Continue cooking gently until the cheese melts and the sauce begins to thicken.
Add spinach: Add the fresh spinach and stir until it wilts into the creamy sauce.
Return the chicken: Place the cooked chicken breasts back into the skillet. Spoon the sauce over the chicken and simmer for another 2–3 minutes so the flavors can come together.
Serve: Garnish with fresh chopped parsley and serve warm with pasta, rice, mashed potatoes, vegetables, or crusty bread.