This is hair ice. It is formed on dead barkless wood and a fungus called Exidiopsis effusa is the main reason.
I found this and many more, during late autumn in a forest in Northern Denmark
Thank you for posting this! I saw several examples of this during the recent freezing weather in the UK, and was confused as to what it was. I don’t recall having seen it before, but then I haven’t lived in a wooded valley during prolonged double-digit negative temperatures before either.
Nice to see the real thing! Lots of people recently down south here in the states posting Verbesina and similar "frost flowers" producing plants during the freeze