The chocolate is mentioned because some time ago people discovered that you can just use a piece of diffraction grating or holographic stickers as mold for molten chocolate and it will transfer the diffraction grating/hologram to chocolate. Now you can buy commercial silicon molds for creating chocolate with holograms, you can also get 3d printer build plates with similar idea. Just reproducing a hologram in DIY environment with easily available household items is unusual, doing it with food items is more amazing. Applied science channel has a video on that as well from few years ago although he wasn't first one to come up with similar idea.

This technique with laser seems to produces the diffraction grating by varying oxide layer thickness not by creating 3d texture so resulting surface is still flat and attempting to use it as mold will not transfer the pattern to chocolate.

The reason many commercially available diffraction gratings have 3d texture (and thus suitable for copying with chocolate) is because stamping a hot piece of metal into plastic is a very cheap way of doing it.