Heat oil and butter in a large deep skillet or Dutch oven over medium-high; add chicken seasoned with salt and pepper. Cook 5-6 minutes until browned all over.
Add onion and mushrooms; cook 4-5 minutes until mushrooms release liquid and onion softens.
Stir in garlic and Italian seasoning; cook 1 minute until fragrant.
Add Marsala; simmer 2 minutes to reduce slightly. Stir in broth, cream, and pasta.
Boil, then reduce heat to medium-low; simmer uncovered 15-18 minutes until pasta is tender and sauce thickened, stirring occasionally.
Stir in Parmesan; adjust seasoning if needed and garnish with parsley before serving.