Extinguish the baking soda in the yoghurt. Add the salt and 1 tbsp oil. Stir well. Add the flour, as much as it'll absorb.
In a separate bowl, beat the feta cheese and eggs. Put them in the dough and stir well with a fork in order to distribute well throughout.
Grease and flour a tray. Pour in the mixture and spread it out evenly.
Smear with an egg yolk and 1 tbsp yoghurt on top. Bake at 392°F (200 °C) to a brown crust.