Cook macaroni according to package directions; drain and rinse in cold water. In a large bowl, combine the evaporated milk, milk, egg substitute and butter. Stir in the process cheese, 1-1/2 cups sharp cheddar cheese and macaroni., Transfer to a 3-qt. slow cooker coated with cooking spray. Cover and cook on low for 2-3 hours or until center is set, stirring once. Sprinkle with remaining sharp cheddar cheese and, if desired, coarsely ground pepper.