While recipes themselves are difficult to copyright, it can be done. However, cooking a copyrighted recipe for profit is no infringement on the copyright. However again, this is no protection from being sued as courts will hear most any case these days. Remember, copyright doesn't protect facts, just the presentation of facts. Recipes are mostly facts.
Reprinting the recipe except for purely personal purposes is a violation of the copyright. So if you are supplying copies of the recipe to your cooks, you're in violation. If they use the original cookbook with your cooks, you would be ok.
There is also the risk that the recipe is patented. You can't use patented recipes for anything without written permission. I believe that the recipe for Coke is patented, for example.
There is a third risk. Mr. Oliver deserves credit for his work. I am certain that Mr. Oliver has trademarked himself. Therefore, to give proper credit on your menu, part of a for profit enterprise, you'll need written permission.
It boils down to needing written permission and likely paying some fee to Mr. Oliver. And that's just good behavior anyway.