Butterfly the chicken breasts by slicing them horizontally through the middle so you have thinner, even pieces. This helps them cook quickly and stay tender. Place butterflied chicken in a bowl and mix with all marinade ingredients. Coat well and set aside for 30 minutes (or up to overnight).
Heat a large deep skillet over medium-high heat. Add the chicken along with all the marinade. Sear for 3–4 minutes per side, until golden on the outside (it does not need to be fully cooked through). Remove the chicken from the pan, cover loosely with foil or a lid, and set aside while you prepare the pasta sauce.
Reduce heat to medium. Add ¼ cup water to the hot pan. Scrape the bottom of the pan with a wooden spoon to release all browned bits.
Build the sauce: Add onion and cook for 2–3 minutes until softened. Add garlic and cook for 30 seconds. Pour in marinara sauce, heavy cream, and remaining chicken broth. Stir in Italian seasoning and bring to a gentle simmer.
Add uncooked pasta directly into the sauce. Cover and cook on medium-low heat for 10–14 minutes, stirring every 2–3 minutes to prevent sticking. Add ½ cup water at a time as needed, up to a total of 2 cups, to keep the pasta mostly submerged in liquid. Cook until the pasta is tender and the sauce is creamy and thickened.
Place seared chicken on top of the pasta. Cover with a lid and cook on low heat for 5–7 minutes, until chicken is fully cooked through. Turn off the heat. Sprinkle with 2–3 tbsp grated parmesan, or serve it on the side so everyone can add as much as they like.
