Greek "pirostiá"

The Neogreek word "pirostiá" should be the word wherefrom the Bulgarian
"pirstija" derives from.
Since I don't have on the table here a Neogreek dictionary and in the
online dictionary the word is not given, I should like to ask if one can
explain what does mean in NeoGreek the word "pirostiá" and the etymology
of this word if available. I souppose this is something related to
"fire" but more it will be unsafe to speculate about:-)
Of course, it is interesting to know which is the meaning in Bulgarian
of the word "pirstija" too.

Many thanks,

Alex