Just my opinion, others might be better informed or have better ideas so take it for what it's worth...
-I don't think picking something that you're passionate about is that important. If you can't be enthusiastic about a topic of your choosing for 10 minutes in a job interview without it being something you're passionate about you have bigger problems in this job interview than this.
-Obviously pick a topic you're knowledgeable about, if they ask follow up questions you should be able to have an answer.
-Pick a topic that fits the time. You don't want to go on for too long (11 minutes is too long), and you don't want to have to cram stuff in there or hurry past important steps because your topic is better suited to a 15 minute presentation. Time yourself, then time yourself again. You can wear a watch and time yourself at key parts of your presentation to make sure you stick to your time during your actual interview as nerves and pressure can mess with your timing. I would try out a few different topics for time (if you have the time for it) and try it out on friends or family to see what they think.
-Try to make your presentation as natural and fluid as possible, if you're confident enough you can improvise some stuff as you go along if they react in a way or another, but have your basic script to fall back on in case you get nervous. It might seem rehearsed, but it's a teaching presentation, not a date. Rehearsed is good.
-Be pedagogical about it. Tell them what you're going to teach them, teach them, then tell them what you taught them. I think this is a lot more important than enthusiasm/passion. If I come in with a wonderful and enthusiastic presentation on how to slice a mango I think most interviewers would realize that my passion is mango cutting and that this doesn't necessarily translate into job enthusiasm. Again, some level of enthusiasm is necessary, but you should be able to muster that. If they're making this a part of the interview I suppose teaching or training is some part of the job or a potential part? If so showing that you can structure and complete a small lesson in a way that facilitates learning is the important bit. I would pick a topic with this in mind, a topic that lets you show that you have these skills.
-Unless asked to I wouldn't put together a power point presentation (if asked to please make sure you can put together a non-gag-inducing presentation, it's not hard, but many people fail). But nothing wrong with a few illustrations or something like that on a few printed pieces of paper if you feel it helps you explain whatever it is you explain. The focus has to be the value to the explanation, not somehow working an illustration or a prop into your little lesson.
-Explain why you say what you say, or how you know what you know. If you hated teachers that would say "because I say so" you weren't alone and a large part of being pedagogical is just that explanation. If you make a claim, support it. This is the best way to make tea? Why is this the best way to make tea? Don't make them ask, give the information. Your personal opinion is not what they will be looking for. If it was me I would probably look to present some kind of scientific documentation or something like that, although perhaps not for the tea.
-A little bit of humour is good, but make sure it's not lame and doesn't become the most important part.
-If it's a skill, you should probably have them try. If you master a skill that you know is quite easy once you master it and not that hard to learn, but that a lot of people think is hard then that might be a decent idea.
