Heat the broiler with a rack 6 inches from the element and toast the bread on both sides until firm and pale gold.
Melt the butter in a saucepan over medium heat, whisk in the flour and cook for 1 minute without browning.
Whisk in the warm milk gradually and simmer for 4 to 5 minutes until the sauce coats a spoon.
Remove the pan from the heat and whisk in 3/4 cup Pecorino, the salt and nutmeg until smooth.
Place each toast in a broiler-safe shallow dish and cover it with 3 ounces turkey and 2 tomato slices.
Spoon the Mornay over each sandwich, scatter on the remaining Pecorino and cross 2 bacon slices over the top.
Broil for 3 to 5 minutes until the sauce bubbles and browns in spots and the turkey layer reaches 165°F.
Rest the Hot Browns for 2 minutes before carrying the hot dishes to the table.