I have made chicken this way many times and I have no difficulty getting a wonderfully crispy skin.
I wonder if you are drying the chicken properly before you attempt to crisp the skin.
I also wonder why you are using butter which is almost certain to burn in this situation.
I also wonder if you are afraid of heat. You should be getting the pan hot before adding the oil and the chicken should make a wonderful sizzling noise when you add it to the hot pan. Those are the thoughts that come to my mind.
edited to add
If you have difficulty determining when the oil is hot enough, get yourself a couple of wooden chopsticks. When you think the oil is good and hot hold the chopsticks upright in the pan so their tips are in the oil. If you see lots of little bubbles around the tips, your oil should be hot enough.
Edited yet again to add this link to Voltaggio's video. The video is in three parts so be sure to watch all three.
