Pat the chicken dry and season both sides with the Italian seasoning, garlic powder, salt and black pepper.
Heat the olive oil in a large skillet over medium-high heat. Sear the chicken for 5-6 minutes per side until golden and cooked through to 165°F (74°C) in the thickest part. Move to a plate and cover loosely.
Reduce to medium heat. In the same pan, cook the garlic and sun-dried tomatoes for 1 minute until fragrant.
Add the chicken broth, scrape up the browned bits from the bottom of the pan, and simmer for 2 minutes.
Stir in the cream and bring to a gentle simmer (do not hard-boil). Add the parmesan and stir until melted and smooth, 1-2 minutes.
Add the spinach a handful at a time until just wilted, about 1 minute. Adjust salt and pepper, and add the red pepper flakes if using.
Return the chicken and any juices to the pan, spoon the sauce over, and simmer gently for 2-3 minutes.
Serve straight from the pan with extra parmesan, over pasta, rice or mashed potatoes, or with crusty bread.