Pre-heat the oven, 200 degrees, lower part of oven only.In a large bowl, mix flour, baking powder, salt and one egg.With hand mixer, beat in enough cold water to make it look like pancake mix, not too thick but not to runny.
Rub the surface of a large tray with margarine and on top of that rub with some olive oil. This way pita will not stick.For the tray, I use the one that came with the oven, so it's the same size as the oven shelf. Using a smaller tray will give you a thicker pie, it's much better if it's kinda thin!!
Next sprinkle the feta all over the surface of the flour mix. Beat the egg, and sprinkle this too.
Finally, sprinkle the olive oil, don't be stingy with the oil, it will be absorbed and makes it tastier.
Place the tray in the very bottom of the oven so that the underside gets crispy. I usually check after about 10mins, using a spatula to lift a corner. If you think it's crispy or browned enough, move the tray to the top so that it gets a nice color, at the same time changing the oven setting to bake top and bottom. Keep an eye on it, some ovens may brown quicker. Remove, cut into squares and enjoy. Can be eaten hot or cold. We prefer hot.