I have made trifles in a similar manner that did not look NEARLY as beautiful as those!
I think that they used ring molds that are lined with parchment paper. That is, the parchment paper lines the ring, perhaps a little taller than the ring mold. Once everything is set, the mold is removed (it easily slides off and the parchment remains) and then the parchment is peeled away.
If you look at the foremost picture, you can see near the top, where the glaze meets the mousse, that there are small "chips" in the mousse where it was pulled away with the parchment. Also, the air bubbles in the mousse are pronounced. If it had been cut or a mold been pulled straight off, the sides would be smeared and the air bubbles would not be visible.