I had a slight frustration with this, I generally keep a lot of tabs open, but once due to an issue fiddling with an extension destroying my existing session, and another due to transferring to a new computer at work, I’ve had to try and restore my Last Tabs / Session data, and each time had to google around and cobble together an answer.

Here it is for those of you searching for the same answer.

If you’ve opened chrome since you’re going to need a backup of your old files (I’ve retrieved this from an Apple Time Machine, or simply the old mac profile ~/Library folder)

For the from backup route, navigate to the following folders in your backup:
Mac – /Library/Application Support/Google/Chrome/Default
Windows – \AppData\Local\Google\Chrome\User Data\Default

And copy the Last Session and Last Tabs files to the same folder on your hard drive, so most likely:
Mac – /Users//Library/Application Support/Google/Chrome/Default
Windows – C:\Users\\AppData\Local\Google\Chrome\User Data\Default

After which you simply need to launch it using the correct launch parameter of --restore-last-session, so:

Mac – Open a terminal and launch using: open /Applications/Google\ Chrome.app --args --restore-last-session
Windows – Edit the shortcut and make sure it’s launching with something like "C:\Users\\AppData\Local\Google\Chrome SxS\Application\chrome.exe" --restore-last-session