01 - Bring a large pot of salted water to a rolling boil. Add the pasta and cook according to package directions until al dente. Reserve ½ cup of the starchy pasta water before draining. Set the drained pasta aside.
02 - While the pasta cooks, season the thinly sliced chicken breasts generously with salt and freshly ground black pepper on both sides. Heat olive oil in a large skillet over medium-high heat. Sear the chicken for 4 to 5 minutes per side until deeply golden and cooked through. Transfer to a plate and keep warm.
03 - In the same skillet, melt the butter over medium heat. Add the chopped onion and sauté for about 2 minutes until softened and translucent. Stir in the minced garlic and cook for 1 minute until fragrant, being careful not to let it brown.
04 - Reduce the heat to medium-low. Pour in the heavy cream and whole milk, stirring to combine. Bring the mixture to a gentle simmer. Gradually whisk in the freshly grated Parmesan cheese, allowing it to melt smoothly into the sauce. If the sauce seems too thick, add the reserved pasta water a splash at a time until the desired consistency is reached. Sprinkle in the dried Italian herbs if using.
05 - Add the cooked pasta and seared chicken back into the skillet. Toss everything together until the pasta and chicken are evenly coated in the creamy garlic Parmesan sauce. Taste and adjust the seasoning with additional salt and pepper as needed.
06 - Serve immediately while hot. Garnish each portion with freshly chopped parsley and an extra dusting of Parmesan cheese if desired. Pair with a crisp white wine such as Pinot Grigio or Sauvignon Blanc.