Start out with a regular french braid on once side, and braid down to the bottom of the hair.
On the other side, start the french braid, but when you get about 3/4 finished with the main braid, bring the right side over into the left braid. I just incorporated it into one of the 3 braiding sections...
Finish the braid all of the way down. You'll end up with one braid on one side of the head.
I just took the braid and twisted it around into a little bun shape, but you could easily do a bun on the side of the head, or just leave that long braid instead. (Or you could tie it off closer to the head and then curl the ponytail for a fancier do...)
Here's how mine turned out- although my hair is not as photogenic as Emma's. :) You can't really tell, but because mine is shorter, it wasn't twisted around as much as Emma's- the one left braid was just pulled over to the right and pinned in place. Also, as the day went on, mine started pulling out a bit because of the shorter hair. It actually ended up looking like one of those super cute really messy braids. We went out on a little date this night, and two of the waitresses asked how it was done.