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 was also gave me insight into her personality and interests.