Melt over over medium low heat in a medium sauce pan. Whisk in flour, cook 1 minute.
Slowly whisk in warm milk. Simmer 5-6 minutes, whisking frequently until thickened.
Place toasts on a large baking sheet, place under broiler for 2-3 minutes to toast. Watch closely!
Top bread with ham and béchamel sauce. Sprinkle generously with cheese.
Place back under broiler until cheese is melted and browned. Serve immediately.