Preheat grill to medium high heat. Clean the grill grates. Cook the chicken breasts (throw them on frozen, no need to defrost!), and cook until the chicken is cooked through and has an internal temperature of 165 degrees, about 15 minutes. Flip the chicken half way through cooking. Allow the chicken to rest for 5 minutes.
Assemble your burger with your favorite condiments, bacon, tomato, avocado, red onion and watercress. Serve.