# Wash the spinach
and chop it, place into a pot. Add finely chopped onion
and vegetable oil on it. Cover the lid of the pot. Steam it over low heat for half an hour, without water addition.
# Pour the milk
into a deep bowl. Add yogurt
, vegetable oil, vinegar, salt and egg on it and mix to make it dough.
# Add flour
into this mixture little by little, while kneading the dough, until it reaches medium consistency and stop sticking to your hands. Cover the dough and rest it for half an hour.
# When the mixture of spinach
cools down, add egg white and mashed feta cheese
# Divide the rested dough into 4 equal pieces. Roll out the first piece of the dough over flour
ed bench by a rolling pin, as thin as you can.
# Spread 2 tbsp vegetable oil all over it. Then, place 1/4 of the spinach
mixture on it and lay over. Roll out the second piece of the dough, and place it over the prepared first one.
# Spread 2 tbsp vegetable oil all over this layer also. Place 1/4 of the spinach
mixture. While the layers superposed, roll it, but not too firmly.
# Repeat the same processes for the remaining 2 dough pieces. Place the prepared 2 rolls over the greased baking tray.
# Spread yolk all over them. Make cuts over the rolls with 1 inch spaces between the each cut, by a knife. Place the tray into the oven, which is preheated to 374 F.
# When the upper sided of the roll shaped boreks turn into red, remove the tray from the oven. When they turn into tepid, slice them from the strings, which you made, before placing them into the oven.
# Serve it warm.