You mean the energy temple boss?
Yeah, that's the thing. After being hit two times by the laser, he learns not to advance beyond it... or does he?
As you already know, in order to activate the laser, you have to charge up a charged attack by holding the mouse button, and release it to hit the white pearl. But... you can hold a charge as long as you like, it won't be released until you let go of the mouse button again.
So what you need to do to hit him a 3rd time, is charge up a charged attack, and then hold it, maneuver so the energy boss will try to grab you, dodge it, and as soon as his arm or mouth is in the lasers reach, then release the charge.
If you don't get what I'm saying, then look at this video
http://www.youtube.com/watch?v=iFCyxXY5MSY And skip right to the part that starts at 7:26 (you don't have to wait for the video to load completely, just click on the time bar where it says 7:26 and the video will start loading from there)