01 - Fill a large pot with water and bring to a boil. Salt generously. Cook pasta according to package directions until al dente. Drain and reserve 1/2 cup of pasta water.
02 - Butterfly the chicken breasts, season both sides with salt, pepper, and Italian herbs if desired.
03 - Heat olive oil in a large skillet over medium-high heat. Add chicken and sear until both sides are golden and internal temperature reaches 165°F, approximately 5–6 minutes per side. Transfer to a plate and cover loosely to rest.
04 - In the same skillet, reduce heat to medium. Add butter and allow to melt. Sauté chopped onion for 2–3 minutes until softened. Add minced garlic, stir, and cook for 1 minute until aromatic.
05 - Pour in chicken broth to deglaze, scraping the bottom of the pan to release any browned bits.
06 - Add heavy cream to the skillet and bring to a gentle simmer. Stir in Parmesan cheese until the sauce is smooth and creamy. Adjust salt and pepper as needed.
07 - Slice the rested chicken breasts thinly. Return chicken to the pan, add cooked pasta, and toss to coat everything in the sauce. Stir in a splash of reserved pasta water as needed to achieve desired sauce consistency.
08 - Stir in chopped parsley. Serve immediately, garnished with additional parsley and extra Parmesan if desired.