Heat the oven to 375°F and boil macaroni until tender; drain.

Melt butter, whisk in flour for 1 minute and gradually add evaporated milk.

Simmer gently until thickened, remove from heat and melt in American cheese and 8 ounces cheddar; season with salt and pepper.

Fold in macaroni and spread in a buttered baking dish, then top with remaining cheddar.

Bake for 20 to 25 minutes until the edges are darkened and the center bubbles.