That happened to me quite a few times. I have one stuck in my 383 head valve cover hole. I'll never use a cheap Chinese Easy Out again. I find better to drill the bolt close, then fold the shell inward or use a tap to chip it up. Sometimes you can drill around the broken piece with a small drill to pick out the hardened steel. In your case, looks like you can attack the broken bolt from the other side. Can't you double-nut it there to screw it upwards?