Gather the ingredients: macaroni, butter, flour, milk, cheese, ground white pepper, cayenne pepper, small onion, breadcrumbs, grated Parmesan, vegetable oil.
Gather the equipment: pasta pot, heavy saucepan, large bowl, cutting board, knives, grater, casserole.
In pasta pot, cook one pound of macaroni.
Cube 12-16 oz of white sharp cheddar cheese
Grate 6-8 oz of yellow mild cheddar
Slice 6-8 oz of yellow mild cheddar
Mince one small onion.
Preheat oven to 400.
In a heavy, medium saucepan, melt 3 T butter over a low heat. When butter is bubbling, add 3 T flour and whisk into a roux (paste). Increase heat to medium low and continue to cook roux until the smell of flour has vanished but DO NOT allow to brown.
Slowly pour in 2.5 cups milk, stirring constantly.
Add onion, white pepper and cayenne pepper to flavor, and let cook until very hot, but do not boil.
Add cubes white sharp cheddar cheese and cook until all cheese is melted, stirring occasionally.
Coat casserole with vegetable oil.
Melt 2 T butter in small cup or bowl, then stir in 1 - 1.5 cups breadcrumbs.
Drain macaroni and dump into large bowl. Pour in cheese sauce and stir until all macaroni is coated.
Transfer half of this mixture into casserole. Cover with a layer of grated yellow mild cheddar.
Pour remaining mixture over that. Arrange sliced cheese on top.
Cover with breadcrumbs and Parmesan cheese.
Baked covered for 30 minutes, then uncover and cook fifteen more minutes, or until bread topping turns golden brown.
Allow to sit at least 20 minutes.