Prep the chicken. Pat the chicken dry. Season both sides with salt, pepper, garlic powder, and paprika.
This helps build flavor and improves browning.
Sear the chicken. Heat the olive oil in a large skillet over medium-high heat. Add the chicken and cook 3–4 minutes per side until golden and just cooked through. Transfer to a plate and tent loosely with foil.
Soften the aromatics. Lower the heat to medium.
In the same skillet, add the diced onion. Cook for 3–4 minutes, stirring to loosen the browned bits. Add the garlic and cook 30 seconds, until fragrant.
Deglaze and start the sauce. Pour in the chicken broth and simmer for 1–2 minutes to reduce slightly.
Melt in the cream cheese. Add the cream cheese cubes.
Stir gently as they melt into the broth to form a smooth base. Keep the heat at medium or below to prevent sticking.
Add dairy and seasonings. Stir in the milk or half-and-half, Parmesan, Italian seasoning, and red pepper flakes (if using). Simmer 2–3 minutes, stirring, until the sauce thickens slightly.
Taste and adjust salt and pepper.
Return the chicken. Nestle the chicken and any juices back into the sauce. Simmer for 2 minutes to warm through and let the flavors blend. If the sauce is too thick, add a splash of broth or milk.
If too thin, simmer a bit longer.
Finish and serve. Sprinkle with fresh parsley or chives. Squeeze a little lemon over the top for brightness, if you like. Serve with pasta, rice, mashed potatoes, or roasted vegetables.