This article adds the required information on how to get grub-efi to work in case of troubles.
After Debian installation re-insert Installer CD/DVD and boot from it.
Choose the rescue menu and select your root filesystem device (the device where "/" and not where "/boot" is on).
Check for mounts:
If this command shows you that /boot is mounted try to verify:
umount /dev/<device where /boot is on>
If this gives you an error, than you know for sure that the information was in /etc/mtab but the device was not mounted.
Now mount your /boot device again:
mount/dev/<device where /boot is on> /boot
Create efi directory:
Mount your hidden efi partition
mount /dev/<hidden efi partition> /boot/efi
Load efivars module
apt-get install grub-efi
Rerun update-grub and grub-install
This will put a new directory in /boot/efi/EFI/ with name debian
Unmount all partitions, exit the terminal and reboot the system.