In this instance, Linda Sue Park together with Lois Lowry.
That's some serious writing firepower there!
Years ago, I took a short workshop with Linda Sue and she explained the way she begins a novel.
This link is from 2000.
I wonder if it still holds true for her process. I bet it does.
One of my favorite parts of this advice:
What I like best about Ms. Lowry's outline is that there is NO step labeled “Theme.” I think she believes as I do: That theme should grow out of the character and the story. If a writer begins with theme, the story is likely to be heavy-handed and messagey ... the kind of book kids run away from. And I'm running right beside them!
(from my desk, my inspiration for today...)