Just guessing, here, but maybe they spread out the chocolate, cut into strips and then used top of a round cutter to do tops? That's the only thing I could come up with.
Just a guess but i would try melting chocolate and spreading it out on a tray with waxed paper on. then take a curved border cutter, use that in a line to get the humps then cut down in lines at the place the bumps are at the lowest point. does that make sense? you could also use chocolate fondant?!