Cook and drain macaroni, place in oven proof casserole. Melt Velvetta, sour cream & cream cheese in the butter. Add evaporated milk. Stir until smooth. Add 1/3 of the mozzarella. Pour over macaroni.

. Sprinkle remaining mozzarella over top. Bake at 375 for 30 minutes or until bubbly. Don't let it get brown on top because the mozzarella won't be stringy.