This is certainly not your average sandwich, and one that does take 25 minutes from idea to plate (10 minutes preparation and 15 minutes cooking), so you should halve the quantities if you are making this as a treat for yourself.
(Chinese Five Spice is more easily obtained than Cajun seasoning.)
Season the chicken breasts with salt, your choice of spices, and pepper. Cook chicken breasts in a nonstick frying pan for five minutes, then turn and cook for about another four minutes until cooked through but still moist and juicy. Now squeeze a little lemon juice over them.
While the chicken is cooking blend the blue cheese and mayonnaise together.
Layer the salad ingredients on top of the slice of bread and slice the chicken thinly and place on top, followed by the blue cheese mayo.
Sandwich together with the remaining bread and eat warm.