Sift the flour twice and mix it with the baking soda. Make a well and place the salt in it. In a separate dish, mix the yoghurt and 3 eggs, add the oil and sugar. Mix this mixture with the flour, adding water until you get a soft dough.
Knead until the dough becomes smooth, begins to bubble and comes off the dish. Roll out a round loaf and decorate the top with various shapes made of dough. Smear it with egg yolk and leave it to stand for half an hour.
Bake in a moderate oven. Once finished, smear the loaf with a little water, wrap it in a towel to cool.