RE: Kyiv perepichka - 30 year of excellent taste

I would recommend explaining what perepichka is, actually. :)
I had to look it up on the Internet, even if the name is a little hint itself for me (and probably not for non-Slavic readers). The pictures are quite small, too.

So, what bun is used here, is it somewhat special?
Are there any other перепички known in Ukraine, so Київська would be not the same as Львовская or something else?
Is it known nationwide, or just a local treat? :)