In a bowl, sift the flour, add the salt and stir. Separately, dissolve the yeast in the warm water, add the sugar and stir until dissolved. Beat the eggs, egg yolks and yoghurt, add them to the flour. Add the dissolved yeast and knead a soft dough.
Cover the bowl with plastic wrap and leave it in a warm area for 1 hour to rise. Sprinkle your counter with flour and knead the risen dough. Cut it into 6 identical parts and form them into balls.
Roll out each ball to a round sheet 13 3/4″ (35 cm) in diameter and arrange them on top of each other, while smearing with the soft butter in between them; don't smear the topmost sheet. Roll out the stacked sheets into 1 large sheet 23 1/2″ (60 cm) in diameter, smear it with the remaining butter and cut it into 16 triangles. Roll these up into scones.
Smear a 10 1/4″ (26 cm) diameter form with soft butter and sprinkle flour. Arrange several scones in a circle along the walls of the form, put the rest in the center of the circle.
Smear the shaped loaf with the beaten egg whites and leave them as is for about 30 min. After the elapsed time, place the form in a preheated 392°F (200 °C) oven to bake for about 40-45 min.
Cover the baked round loaf with a clean towel to smother and soften it.