Photoshop released a tutorial yesterday on how to do this effect exclusively in Photoshop and I got a question from my dear YouTube friend 'YozCreative' about how to do this in After Effects. So I'm working on a little tutorial and this is the result of my efforts. It's really very easy to do. All you have to do is copy the footage so you have two layers and then put one or more masks on the top layer and animate the mask path over time. Freeze the bottom layer at a frame of your choice using: Composition - Time - Freeze Frame.
Tutorial will follow shortly.
Btw, I've graded the footage with Magic Bullet Looks2 to look like the movie Amelie Poulian :)