01 - Season both sides of each chicken breast generously with salt, black pepper, and Italian seasoning, pressing the spices gently into the meat to adhere.
02 - Heat olive oil and butter in a large skillet over medium-high heat until butter melts and foams subsides. Add chicken breasts and cook for 5–7 minutes per side until golden brown with an internal temperature of 165°F. Transfer chicken to a plate and tent loosely with foil.
03 - Reduce heat to medium. Add chopped onion and minced garlic to the same skillet; sauté for 2–3 minutes until fragrant, translucent, and just beginning to brown, stirring frequently to prevent burning.
04 - Pour in chicken broth, using a wooden spoon to scrape up any browned bits from the bottom of the skillet. Let simmer for 2 minutes until slightly reduced.
05 - Stir in heavy cream and grated Parmesan cheese, whisking continuously until cheese melts completely and sauce becomes smooth. Simmer gently for 2–3 minutes until slightly thickened and coating the back of a spoon.
06 - Return chicken breasts to the skillet, turning to coat completely in the sauce. Simmer for 3–5 minutes until chicken is heated through and flavors meld. Garnish with fresh parsley and additional Parmesan. Serve immediately.