Put the feta cheese in a bowl, the baking soda in the yoghurt, the salt in the flour. Next, mix all of these together, stir until you obtain a very thick mixture.
Scoop from the mixture with a spoon, put it in a plate with flour, finish shaping carefully, male a hole in the middle, add a little butter.
Arrange all of the pitas in a tray, smeared with oil. Bake in a preheated 347°F (175 °C) oven until ready.