Drop the box of tortellini into a pot of boiling salted water. Place the Alfredo mix, the powdered milk and the water in a saucepan and mix until blended. Over medium heat, stir constantly while bringing mixture to a boil. While tortellini and Alfredo sauce are cooking, pour hot water over the sun-dried tomatoes and rehydrate them until soft (about the same time as the tortellini takes to cook). When cooked, drain tortellini and add to Alfredo sauce. Add sun-dried tomatoes and prosciutto, toss and sprinkle with Parmesan.