Beat 4 eggs with the yoghurt, to them add the crumbled feta cheese, oil and 1 2/3 cups (400 ml) carbonated water.
In an oiled oven dish, arrange 2 layers of phyllo pastry sheets after tearing them into pieces. Then pour on a ladle of the mixture and arrange another 2 layers of phyllo pastry sheets - until you're out of mixture and sheets; be sure to finish off with 2 layers of phyllo pastry sheets.
Cut it into squares and pour on a mixture of the egg beaten with the remaining carbonated water.
Sprinkle with sesame seeds and put butter in several places.
Bake in a preheated 356°F (180°C) oven until ready.