I've just googled the same question with the exact same cake in mind and this thread came up! Have you worked out how it's done?
Has it not been sprayed with a metallic paint then hand brushed with pearl??
AThe luster dust is mixed with vodka and painted on. I normally airbrush but I don't think it would give you that same look
Just so long as we all know luster dust is not edible. At least none of mine is. I don't have every color, but all of mine say, "non-toxic". There are some edible dusts, but they don't look anything like the silver in Sammy's link. And Super Pearl, Pearl Dust, mentioned twice in the other link, is not edible.
Ironically, it's the one dust that CK products sells by the pound. Probably better off with one the edible dusts (which are not as shiny) or PME pearl spray.
AYes OP, the one I dust do have says non-toxic, aand I have only used it on fondant, or Gumpaste toppers that stubb wont be eaten. So do look into sprays. I really like this look and it was one of the reasons I invested in an airbrush machine.
I have done this by brushing on PME pearl spray and looks really good.