If you have ever been to Psyrri, you must have noticed that there is one pie shop in the central Piazza (which is called Plateia Iroon, Square of Heroes). I have seen it so many times, but never taken interest in it, because, when I go to Psyrri, I am either looking for a restaurant or a cafeteria, and never a pie shop.
What made me change the idea was a photo of the interior that I saw on Foursquare (which is, by the way, a terrific website/mobile software if you like to get information about restaurants and cafeterias; information there is not always credible, but it is definitely a happy hunting-ground).
It has a very strange shape and looks like a mixture of a medieval castle and an underground meeting hall of Mithraic cult.
I bought a portion of cheese bougatsa (savory) for 1.80 Euro. It is sold by a kilo, so the price is not fixed.
At the beginning, I found it too salty, but then got used to it. The fyllo was pretty good, although it wasn't so fresh when I bought it.
Apart from bougatsa (sweet cream or savory cheese), they sell also a variety of pies. When I saw, they had a spinach pie, koulou dough cheese pie, and small cheese pies (tyropitakia).
The staff was friendly and it is open 24 hours.
It is a nice spot for a snack when you are in the area.
Thessaloniki stou Psyrri - Η Θεσσαλονίκη στου Ψυρρή
Plateia Iroon 1, Psyrri, 10554 Athens
Πλατεία Ηρώων 1, Ψυρρή, 10554 Αθήνα