Friday Candy Video

We've all seen that internet meme where they chop up a chocolate bar a certain way, remove a square, and are then able to rebuild a chocolate bar of the same size.  Now someone has done a video of this crazy math puzzle, and I still can't figure it out.  I've been tempted to try this trick myself, the problem is every time I open a chocolate bar, I just end up eating part of it.

CC