Yes you can cook chicken in the steamer, but a few points worth considering first. What size is the chicken breast and is it boneless? I am presuming it is so I would say for approx 140g weight, this would take 15-20 minutes. Make a small incision in the thickest part and check that the juices are clear, if not carry on cooking for a further 5-8 minutes. A good tip is to try and flatten out the breast slightly so that it is roughly the same thickness. It will then cook evenly and take less time too.