I foolishly went browsing in my EFI partition on my Ubuntu (Elementary OS) laptop and decided to delete the Ubuntu folder. This made my laptop unbootable. This was my procedure to bring it back to life:

Boot into Ubuntu Live CD / USB environment

Decrypt LUKS encrypted drive (https://blog.sleeplessbeastie.eu/2015/11/16/how-to-mount-encrypted-lvm-logical-volume/)

sudo fdisk -l
#Determine encrypted partition is /dev/nvme0n1p3 because it's the largest
sudo cryptsetup luksOpen /dev/nvme0n1p3 encrypted_device
sudo vgchange -ay

Mount encrypted drive & chroot (https://askubuntu.com/questions/831216/how-can-i-reinstall-grub-to-the-efi-partition)

sudo mount /dev/elementary-vg/root /mnt
sudo mount /dev/nvme0n1p2 /mnt/boot/
sudo mount /dev/nvme0n1p1 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt
sudo grub-install
update-grub  

#end chroot & unmount
exit
cd
for i in /mnt/dev/pts /mnt/dev  /mnt/proc /mnt/sys /mnt/run /mnt/boot/efi /mnt/boot /mnt; do sudo umount $i;  done