Season chicken with salt and pepper.
Melt 1 tablespoon butter in a large skillet until foaming. Cook chicken until lightly browned. Transfer to plate when done.
Boil water and cook pasta according to the directions.
Melt additional 1 tablespoon of butter in skillet, add garlic, mushrooms and onion and cook for about 6 minutes.
Add cooked chicken back into the skillet.
Add the Marsala, chicken broth and cream and bring to a boil. Simmer until sauce is slightly thickened.
Drain pasta and reserve ½ cup cooking water.
Return the pasta to the pot with the remaining 3 tablespoons of butter.
Add the mushrooms and chicken mixture and ½ cup of Parmesan cheese and cook until the pasta has absorbed some of the sauce, about 1 minute, adding the reserved cooking water as needed.
Season with salt and pepper and serve with additional Parmesan cheese and a garnish of chopped parsley.
