01 - Bring a large pot of salted water to a boil. Add pasta and cook according to package instructions until al dente. Drain, reserving 1/2 cup of the cooking water.
02 - Butterfly chicken breasts and season both sides with salt, pepper, and dried Italian herbs if using.
03 - In a large skillet over medium-high heat, heat olive oil. Add chicken and sear until golden brown and cooked through, about 5 to 6 minutes per side. Transfer to a plate, cover loosely, and let rest.
04 - Reduce skillet heat to medium and add butter. Sauté onions for 2 to 3 minutes until softened. Add minced garlic and cook until fragrant, about 1 minute.
05 - Deglaze the skillet with chicken broth, scraping up any browned bits from the pan.
06 - Add heavy cream to the skillet and bring to a gentle simmer. Stir in Parmesan cheese until smooth and creamy. Season with additional salt and pepper to taste.
07 - Slice the rested chicken breasts thinly. Return chicken to the skillet along with the cooked pasta. Toss everything to combine, adding some reserved pasta water as needed to reach the desired sauce consistency.
08 - Stir in chopped parsley and serve immediately, garnished with extra parsley and Parmesan cheese.