grub-efi configuration [was: Mac Pro, Debian/OS X dual boot, EFI - I'm missing something]

[Brian Flaherty <bxf4@yahoo.com>]

So, I've made some progress getting Debian booting on my old Mac Pro. 
Right now, here's the hang-up and I'm not sure how to proceed.

I'm
 using rEFInd to choose what to boot. It finally finds my Debian 
installed grub efi image, however, there's something wrong in a path and
 it dumps me at grub-rescue. Essentially, the problem there is that the 
directory to the modules it needs to load is lacking a /. When I land in
 grub-rescue this is my prefix:

(hd1,gpt1)boot/grub

It complains it cannot find insmod normal to continue. If I set prefix to this:

(hd1,gpt1)/boot/grub

then 'insmod normal' and normal work and dump me at a grub prompt.

I
 haven't yet succeeded in booting the system from that grub prompt 
either, but I'm hoping that if this prefix is corrected, maybe it'll 
work.

I continue to boot using the supergrub cdrom, telling it to
 find grub.cfg, then selecting my kernel. I used to have to edit that 
text, but now I don't need to. Updating to grub-efi in sid seemed to fix
 something.

Any guidance on correcting prefix or other tips to get this working would be great. Thanks for your time.