For the bacon: In a large skillet, scatter the lardons and turn on the heat to medium. Cook until crisp. Make sure to reserve 2 tablespoons of the bacon fat in the skillet. Then drain the crispy lardons on a paper-towel-lined plate.
For the mornay sauce: In the same skillet, add the butter to the bacon fat and set over medium heat. Add the flour and whisk until blonde, 2 to 3 minutes. Slowly whisk in the milk until combined. Add in the gruyere and nutmeg, and simmer until thick, 5 to 7 minutes. Season with salt and white pepper.
For the sandwich build: On 4 of the slices of toast, layer 2 tomato slices, top with a quarter of the turkey and then the second slice of bread. Ladle lots of mornay sauce over top. Top with a nice pile of bacon and fresh parsley.
Recipe courtesy of Jeff Mauro