Its got to be Hokkaido for big pow or Nagano is also very good but not quite as much consistency with the snow.
The post above shows a link to a thread where this is explained in much more detail
check this guy out
http://www.snowboardingforum.com/asi...tml#post433492
he might hook you and your girlfriend up for a 2 week stay if he can't find a share partner (I suspect he won't this late).