Ummmm.....well....cooks are people.......right?
What difference does it make if they are a cook? I don't get that.
Does anyone WANT to lose their job really? I'd say no -- for the most part at least.
It would have helped if you'd have like....I dunno...added like....information in your question so we knew what situation this is all about, but since there's none, I can only say be polite, firm and sympathetic, as well as supportive. Don't be degrading or harsh. Have a witness or two there, and be clear with when you'd like them to leave, and make sure you pay them to date, or solemnly promise to send their check to them.
You may want to consider having someone else do this, because it's obvious that information and communication skills are not your bag man.