Toast the slices of whole wheat bread until golden brown.
Spread 1 tablespoon of mayonnaise on one side of each slice of toasted bread.
On the first slice of bread, layer half of the turkey breast, followed by 2 slices of bacon, 1 slice of cheddar cheese, and a few slices of tomato. Season with salt and pepper.
Place the second slice of bread on top, mayonnaise side up. Spread 1 teaspoon of Dijon mustard on this slice.
Layer the romaine lettuce, the remaining turkey, the second slice of cheddar cheese, and the rest of the bacon.
Top with the third slice of bread, mayonnaise side down.
Secure the sandwich with toothpicks at each corner and slice the sandwich into quarters for easier handling.
Serve immediately with your favorite chips or a side salad.