Find latest save file you manually made, which will looks like this:

C:\Users\[YOURNAME]\AppData\LocalLow\World 2 Studio Inc\Chef RPG\FullData\SaveSlot[NUMBER]

put all current staff you have in unassigned staff slots and back up save file after

extract packed file to anywhere, then drag and overwrite current file with that thing. 

if done right, your save folder will still look like the following, but with the new staff file having overwritten the old staff file:

C:\Users\[YOURNAME]\AppData\LocalLow\World 2 Studio Inc\Chef RPG\FullData\SaveSlot[NUMBER]\UnassignedStaffData.dat

Do note all old staff must be in unassigned slot prior to this for it to work, and you must have already hired atg least one of each type of staff