Source:An Evening with Harry, Carrie and Garp

From UnknowableWiki

Full transcript here.

Hermione

Nina: I just wanted to know what Hermione would see if she looked into the Mirror of Erised?

J.K. Rowling: Well, (big grin from Jo, crowd laughs and applauds) at the moment, as you know, Harry, Ron, and Hermione have just finished their penultimate year at Hogwarts and Hermione and Ron have told Harry that they're going to go with him wherever he goes next. So at the moment I think that Hermione would see most likely the three of them alive and unscathed and Voldemort finished.

But I think that Hermione would also see herself closely entwined... with... another... person (crowd roars and applauds loudly). I think you can probably guess who. Thank you, very good question. I've never been asked that before. Now we have another.

Potions

Unknown (1): Can muggles brew potions if they follow the exact instructions and they have all of the ingredients?

J.K. Rowling: Well, I'd have to say no, because there is always... there are magical component in the potion, not just the ingredients. So, at some point they will have to use a wand. I've been asked what would happen if a Muggle picked up a magic wand in my world, and the answer would probably be something accidental... possibly quite violent. Because wands, in my world, is merely a vehicle, a vessel for what lies inside the person. There is a very close relationship -- as you know -- between the wand that each wizard uses and themselves. In fact, we'll find out more about that in book 7 (crowd applauds).

For a muggle you need the ability, in other words, to make these things work properly but you're right and I think that's an interesting point. Potions seems, on the face of it, to be the most Muggle-friendly subject. But there does come a point in which you need do more than stir. Thank you, good question.

Wandmakers

Samantha: In the wizarding world there are many wandmakers, Ollivander's being the one we're most familiar with. How come Ollivander chose the three magical cores for the wands he makes to be phoenix feather, unicorn hair, and dragon heartstring? And how come he decided that these are the three most powerful cores as opposed to others such as veela hair?

J.K. Rowling: Good question. Well, it is true that there are several wandmakers and in my notes about Harry I have many different cores for wands. Essentially I decided Ollivanders was going to use my three favorites. So Ollivander has decided that those are the three most powerful substances. Other wandmakers might choose things that are particular to their country, because countries as you know in my world have their own particular indigenous magical species. So Veela hair was kind of obvious for Fleur's wand. But um, yeah, good question. I've never had that one before (crowd applauds).