Not entirely sure it's disco dust, but it looks too sparkly to be anything I'd want to put in my mouth.
Neighbor down the street gave me a plate of baked goods for Christmas. Planning on reciprocating sometime before Epiphany (remember: think liturgically, not commercially, because liturgically speaking, it's still Christmas until Epiphany). In general, the ones I tasted weren't bad, but neither were they as good as what I bake. One of them appears to be some sort of frosted shortbread, with what appears to be the dreaded disco dust atop the frosting.
Is there an easy way to tell whether it's disco dust, or something that's actually edible? Maybe scrape off a bit, and see if it dissolves in water?