Cook macaroni according to package directions. Meanwhile, let the cheeses and butter stand at room temperature. Drain macaroni; transfer to a very large bowl. Add 1-1/2 cups of the shredded cheddar, the cheese product, and the butter to the hot pasta, stirring well. Set aside.
In a medium bowl, whisk together eggs, milk, cheese dip, and white pepper until combined. Stir egg mixture into macaroni mixture. Transfer mixture to a 13x9x2-inch baking dish (3-quart rectangular) spreading evenly.
Bake, covered, in a 325 degree F oven for 25 minutes. Uncover and stir well. Sprinkle with the remaining 1/2 cup shredded cheddar. Bake, uncovered, 15 to 20 minutes more or until cheese is melted and mixture is heated through (160 degrees F). Let stand 10 minutes before serving. Makes 8 to 10 servings.