Cook the macaroni in a large pot of salted water following the directions on the box for al dente. Do not over cook. Rinse well with cold water and drain well.
In a 6-quart crock pot whisk the evaporated milk, the beaten egg and the melted butter until combined.
Place the cooked elbow macaroni into the crock pot. Add the shredded cheese, reserving ½ a cup to use as a topping. Mix with a large spoon.
Add the cubed Velveeta cheese to the crock pot and mix until the cubes are evenly dispersed.
Place the lid on the crock pot and cook on low for 2 hours. Half way through stir the ingredients to prevent the cheese from scorching onto the sides of the crock pot. Continue to cook.
15 Minutes before serving sprinkle the reserved ½ cup of shredded cheese over the top and recover.
Serve when the cheese topping has melted.
