01 - Pat chicken breasts dry with paper towels. Season generously on both sides with salt, pepper, and Italian seasoning, pressing the spices into the meat to adhere.
02 - Heat olive oil and butter in a large skillet over medium-high heat until butter foams. Add chicken breasts and cook for 5-7 minutes per side until golden brown and internal temperature reaches 165°F. Transfer chicken to a plate and tent with foil.
03 - Reduce heat to medium. Add chopped onion and minced garlic to the same skillet, stirring constantly for 2-3 minutes until fragrant, translucent, and softened, being careful not to brown the garlic.
04 - Pour in chicken broth, using a wooden spoon to scrape up any browned bits from the bottom of the skillet. Let the mixture simmer for 2 minutes to reduce slightly and concentrate flavors.
05 - Stir in heavy cream and grated Parmesan cheese, whisking continuously until the cheese melts and the sauce becomes smooth and velvety. Simmer gently for 2-3 minutes more until slightly thickened and coating the back of a spoon.
06 - Return the seared chicken breasts to the skillet, turning to coat thoroughly in the sauce. Simmer for 3-5 minutes, spooning sauce over the chicken occasionally, until the chicken is heated through and flavors have melded.
07 - Transfer chicken and sauce to a serving platter or individual plates. Sprinkle generously with fresh chopped parsley and additional grated Parmesan cheese. Serve immediately while hot, accompanied by your choice of sides.