Your system would continue to work as long as you don't turn it off. So no matter what you do, keep it on until you restored your /boot
Recovering it should be straightforward, assuming you didn't put custom files directly to /boot.
Just reinstall the linux kernels using apt. Then manually run grub-install with appropriate parameters. Finally, run update-grub or grub-mkconfig to recreate the grub config.
If the system is turned off, you can use live USB and chroot to it to properly install the kernel packages.
Can't find an article for it at the moment, but I can tell you real quick how I would've done it.
Use aptitude and look for linux-image-amd64 or something under Installed -> kernel. The exact name might be a bit different.
View the package and look under the Version and check out the one that's marked 'i' (for installed). Select that package and mark it to reinstall (shortcut 'L').
Then finally execute it (shortcut 'g' and then 'g' again).
Assuming the boot partition is still there and mounted. Just empty. If it were me I would try to reinstall grub2 and kernel packages. I don’t know what errors I would encounter trying it, so that would be the next hurdle.
I'm not familiar with Debian. On arch you could just run the package manager to reinstall linux (kernel) and run grub-install with all the usual commands.
I use systemd-boot now so I might be rusty on that. I don't know if it's faster but it feels faster and I don't really care about dual booting.
I made the mistake of putting my timeshift backup on the same disk as the data and kept having it fill my drive to 0bt and crash plasma. Of course I do something this idiotic the one time it's disabled