Cook and drain macaroni, place in oven proof casserole. Melt Velvetta, sourcream & 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 minutesor until bubbly. Don't let it get brown on top because the mozzarella won'tbe stringy.