Boot dell in uefi mode from usb stick

[John Frankish]

I'm not sure if this is possible, but I've been trying to boot a dell laptop 
(latitude e6220) in uefi mode from a usb stick without success.

Using:

$ sudo grub-install --target=x86_64-efi --boot-directory=/mnt/sdc1/efi 
--removable
Installation finished. No error reported.

..but on booting the dell in uefi mode, no bootable device is found. Needless 
to say, it will boot from a usb stick in legacy bios mode.

Does anybody know if the above is possible?