Bring a large saucepan of salted water and a tablespoon of oil to a boil. Add the macaroni and cook until slightly al dente, about 10 minutes. Drain and set aside.
Whisk the eggs in a large bowl until frothy. Combine the processed cheese, butter, and 2 cups of half-and-half in a large bowl.
Add the warm macaroni, tossing until the cheese has melted and the mixture is smooth. Add the remaining 4 cups of half-and-half, 3 cups of sharp yellow cheddar cheese, the remaining grated cheeses, and seasoning salt and pepper, tossing until completely combined.
Pour mixture into 4 au gratin dishes, with the remainder in a casserole, and bake for 30 minutes. Sprinkle remaining 1 cup of sharp yellow Cheddar cheese on top and place under broiler until golden brown. Serve hot.
A viewer or guest of the show, who may not be a professional cook, provided this recipe. It has not been tested for home use.