I would create an invoice using whatever the fmv is of the services rendered and reach out to management/owners. If that doesn’t work after a few tries, reach out to the dept of labor. I just think it’s the chef that should have to suffer, not the entire restaurant.

Edit: just noticed Sally O’s is hiring a sous. OP’s friend should apply. Seems like a great place to work plus they’re on their way to making their own little empire - aka great opportunity for advancement.