Preheat oven to 350. Spray a 9 x 13 baking dish with cooking spray.
Cook pasta until al dente. Drain and set aside.
In a large skillet over medium heat, add olive oil and prosciutto. Cook until lightly crisp on the edges, about 5 minutes. Remove the prosciutto to a paper towel lined plate. In the same skillet, add the mushrooms and garlic. Cook until mushrooms darken slightly and juices are released. Remove to a plate.
In the same saucepan, melt the butter. Whisk in the flour and cook for 1 minute or until bubbly. Stir in the Marsala and bring to a boil for 1 minute. Add chicken broth and bring to a boil. Whisk in 1/4 cup of the parmesan until melted. Remove from heat and add cream and milk. Stir in mushrooms, prosciutto and chicken.
Add pasta to the baking dish. Top with sauce and lightly mix into the pasta. Top with reserved parmesan cheese. Bake uncovered for 20 minutes or until the cheese melts and starts to turn golden.