01 - Bring a large pot of salted water to a boil. Cook the pasta according to package instructions until al dente. Drain and reserve 1/2 cup of pasta water.
02 - Butterfly chicken breasts and season both sides generously with salt, black pepper, and Italian herbs if desired.
03 - Heat olive oil in a large skillet over medium-high heat. Sear chicken breasts until golden and fully cooked, about 5 to 6 minutes per side. Remove to a plate, cover loosely, and let rest.
04 - Reduce skillet heat to medium. Add unsalted butter and sauté chopped onion for 2 to 3 minutes until softened. Add minced garlic and cook until fragrant, about 1 minute.
05 - Pour chicken broth into the skillet, scraping up any browned bits from the bottom.
06 - Stir in heavy cream and bring to a gentle simmer. Add grated Parmesan, stirring until the sauce is smooth and creamy. Season sauce with more salt and pepper as needed.
07 - Slice chicken breasts thinly. Return chicken slices to the skillet with the sauce, add cooked pasta, and toss to combine. Incorporate a splash of reserved pasta water to adjust sauce consistency.
08 - Fold in chopped parsley and serve immediately. Garnish with additional parsley and extra Parmesan before serving.