re: How do you achieve this snowy cake look?

I agree that it looks a bit like the magic sparkles sweetheaven posted. Wilton also makes something similar called “cake sparkles” They come in a variety of colors including white which don’t have the rainbow look those magic sparkles seem to have.

White sanding sugar would also give a similar effect, with in my opinion, more of a crystal/ice look rather then a fluffy snow look of the cake sparkles.