Unlike a backflip, or a 360, a cork 180 is a rotation that cannot be done with an evenly weighted object. A skier has his weight concentrated in his feet. When someone carves the lip of a jump and gets into that cork position, the only thing bringing them back is their natural weight.
Therefore, there is no way to set a rotation that will cork you for a 180 rotation, uncork, then recork for another 180 and uncork