Heat olive oil and butter in a large, deep skillet or Dutch oven over medium-high heat, then add the chicken pieces seasoned with salt and pepper, cooking for 5-6 minutes until browned on all sides.
Add the diced onion and sliced mushrooms to the pan, cooking for 4-5 minutes until the mushrooms release their liquid and the onion softens.
Stir in the minced garlic and Italian seasoning, cooking for 1 minute until fragrant.
Pour in the Marsala wine and let it simmer for 2 minutes to reduce slightly, then add the chicken broth, heavy cream, and pasta, stirring to combine.
Bring to a boil, then reduce heat to medium-low and simmer uncovered for 15-18 minutes, stirring occasionally, until the pasta is tender and the sauce has thickened.
Stir in the Parmesan cheese, adjust seasoning if needed, and garnish with fresh parsley before serving.