What's a Louisville hot brown?

The Hot Brown is an open faced sandwich that is a local speciality throughout Kentucky.   It was originally served in 1926 at Louisville's Brown Hotel.  The sandwich is a spin on the traditional Welsh Rarebit.  It's turkey breast, served open face on white bread, topped with Mornay sauce and run under the broiler until hot and bubbly.  Some variations include ham with the turkey, as well as pimentos or tomatoes.