Make a mornay sauce by cooking the butter and flour in a saucepot for 2-3 minutes, or until you notice a nutty aroma. Slowly add the heavy cream, whisking constantly to avoid lumps. When it bubbles,whisk in the cheese. Add white pepper and salt to taste. Remove from heat and set aside.
Layer bread slices with desired amount of leftover turkey and tomato slices. Toast for 4 minutes in a toaster oven.
Top with the mornay sauce and some extra grated cheese. Broil open-faced sandwiches until browned in a toaster oven or broiler. Top each sandwich with two slices of bacon and minced parsley.