This question will help you assess a candidate's ability to explain a concept they know intimately to someone who isn't as familiar with it. If their hobby is training for a marathon, ask them what advice they'd give you if you woke up one day deciding you wanted to train for a marathon. Are they able to communicate it clearly?

One candidate taught me how to make tagliatelle, which is hand-cut Italian pasta. She gave me the full run-down on how you make the noodles, how you form them and cut them, and which ingredients go into the sauce. She relayed the step-by-step process to me in a way that was very clear and understandable. I felt like I could've gone home and made tagliatelle myself. Not only did this tell me she knows how to convey information clearly, but it also gave me insight into her personality and interests.