How to migrate BootCamp to Parallels VM?

This is a very basic question and must have been asked 1000 times, though a search doesn't turn it up, so I ask again:

How to you take a functioning BootCamp installation and make it into a Parallels virtual machine?

I think this is readily done with VMWare Fusion, and I think there is a path for converting a Fusion VM to a Parallels VM (could be wrong about this), so in the worst case one could use VMWare Fusion to convert BootCamp install to a Fusion VM, and then convert the Fusion VM to a Parallels VM.

Has anyone done this with either system?