Prep the chicken: Pat chicken dry with paper towels. Season both sides generously with Italian seasoning, salt, and black pepper.

Sear the chicken: Heat olive oil or butter in a large skillet over medium‑high heat. Add chicken and sear for 3–4 minutes per side, until golden brown. Remove chicken and set aside.

Sauté garlic: In the same skillet, reduce heat to medium. Add minced garlic (and optional mushrooms, if using) and sauté for 30–60 seconds until fragrant.

Make the sauce: Add cubed cream cheese to the skillet, whisking until melted and smooth. Pour in heavy cream and chicken broth, stirring to combine. Simmer for 2–3 minutes until slightly thickened. Stir in Parmesan cheese until melted.

Simmer chicken in sauce: Return chicken to the skillet, nestling it into the sauce. Spoon sauce over the top. Reduce heat to low, cover, and simmer for 8–10 minutes, or until chicken is cooked through (internal temperature 165°F / 74°C).

Add cheese and veggies: Sprinkle mozzarella over the chicken. If using spinach or sun‑dried tomatoes, stir them in now. Cover for 1–2 minutes until cheese melts and spinach wilts.

Rest and serve: Remove from heat and let rest for 2–3 minutes. Slice chicken into thick pieces (“pillows”) and serve with extra sauce spooned over the top.