Dissolve the baking soda in the yoghurt until it becomes effervescent. Beat 3 eggs. To them, add the yoghurt with the baking soda, oil, crumbled feta cheese (optional savory) and sifted flour.
What you end up with is a medium-thick dough. Lay it out in an oiled oven dish and smear it with the beaten egg. Sprinkle with sesame seeds. Bake at 356°F (180°C) for about 30 min. Check to see if it's baked with a toothpick.