Preheat oven to 325 degrees. 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 cheese, the cheese product, and the butter to the hot pasta; stir well to combine. Set aside.
In a medium bowl whisk together the eggs, milk, cheese soup, and pepper until smooth. Stir egg mixture into macaroni mixture. Spoon macaroni mixture into a 3 quart casserole dish.
Cover and bake for 25 minutes. Uncover and stir well. Sprinkle evenly with the remaining 1/2 cup shredded cheddar cheese. Bake, uncovered, for 15-20 minutes more or until heated through and cheese melts.