Migrate Mac to OSX virtual machine

I need to be able to run a virtual version of OS X Mountain Lion on my El Capitan machine. When you do this using the OS X restore volume, it uses the El Capitan restore volume. I physically rebooted into Mountain Lion and created the virtual OS X drive there. When selecting the restore volume option, Parallels would only allow a full Mountain Lion download from Apple. Once this was installed on the virtual volume I tried to access Migration Assistant to bring this fresh install in parity with the physical Mountain Lion volume but was unable to connect with the drive.
I was told that I could create an OS X virtual machine and then migrate the settings from a physical startup drive. After trying everything I could think of, I finally found a place in the documentation saying that the virtual machines only works with virtual disks. I seem to remember earlier versions of Parallels that would allow access to whatever physical drives you have. I have Sharing set up to see all disks, etc.

 

It looks like a similar post is elsewhere (without a solution) but I can't figure out how to remove this post. Sorry.