How to make
Dissolve the yeast in a little cool water. Knead a moderately stiff dough with 1 1/2 cups of cool water, the oil, vinegar, egg, dissolved yeast and a pinch of salt. Let it rise for about 30 minutes.
Meanwhile, clean the spinach and blanch it in salted boiling water. Then drain, cool it slightly, cut it in small pieces and mix it with 1 tablespoon of oil, feta cheese and the 2 eggs. Divide the dough into 6 parts, divide each of those into 3 balls and roll them out into small pitas.
Butter every 3 rolled out pitas and stick them together. Roll out the first layer of 3 pitas by hand to the size of the tray in which you will bake the pierogi (about 17 3/4″ (45 cm)). Roll out the second one the same way, put it on top of the first and sprinkle it lightly with oil.
Spread half of the spinach filling on top. Arrange the third and fourth layers on top in the same way with a little butter in between. Distribute the spinach on top and finish off with the fifth and sixth stretched out layers.
Cut the Russian pierogi with spinach into squares, add the remaining oil, brush with a beaten egg and put them to bake in a moderate oven.
