1. Preheat oven to 350°. Prepare pasta according to package directions. Meanwhile, melt butter in a large skillet over medium-high heat; add mushrooms and prosciutto, and sauté 5 minutes.
2. Stir together mushroom mixture, chicken, next 5 ingredients, and 1/2 cup cheese; stir in pasta. Spoon mixture into a lightly greased 11- x 7-inch baking dish; sprinkle with remaining 1/2 cup cheese.