There's a patent for casting holograms on chocolate by the same process. (Holograms rely on the same constructive interference effect as diffraction gratings). You need enough sugar in the mix to produce a hard shiny surface to the chocolate.
You can also cut a record on chocolate, but you don't get more than a couple of plays before the needle wears away the grooves.
It was Scientific American. When I was an unemployed pre-internet late-teen, I went through my local library's entire collection, right back to the first Mathematical Games column, and photocopied everything I found interesting. That was one of the articles I snagged.
I did successfully make some iridescent chocolate after that, with a diffraction grating I bought from Edmunds Scientific as a mould.
By the by, you may be interested in this: https://www.litiholo.com/ I'm probably going to buy one at some point.
You can also cut a record on chocolate, but you don't get more than a couple of plays before the needle wears away the grooves.