You could look at a more complicated piece of code, let them think about it for a bit, and if they don't have that aha moment you can still discuss it with them

You could look at a more complicated piece of code, let them think about it for a bit, and if they don't have that aha moment you can still discuss it with them. For example, pick a problem you someone on your team struggled a bit with, something that you wouldn't necessarily expect a candidate to solve during an interview, and discuss solutions with them. I think you could learn a lot about the interviewee this way.