This sandwich is called a Hot Brown, and I think sometimes chicken or other meat is used to make it? Turkey works just fine, though. This was a great after-Thanksgiving meal because I had so much leftover bacon from rendering fat for the Andouille sausage stuffing. Is that a good thing? Eh, bacon is always a good thing.
The assembly of the sandwich is quite straightforward. One takes the leftover turkey, puts it on a slice of toast, tops with mornay sauce, tops with slices of bacon, and edges the whole mess with more toast slices and tomato slices. Then, pop the whole thing in the broiler. Only, watch the Hot Brown closely, as if one has a rather overenthusiastic broiler, one may end up having to replace some of the toast slices!

Mornay sauce: make a roux from 4 T butter and 4 T flour. Off heat, whisk in 1 3/4 c milk and 3 T parmigiano reggiano. Return to heat, cook, whisking constantly, until thick.

What can Brown do for you?