How to make
Activate the yeast with the sugar and part of the milk. Once it becomes effervescent, add the rest of the milk, yoghurt, egg, egg white and 1/3 of the oil.
Once everything is mixed well, add the flour and salt a little bit at a time until you get a soft, sticky dough. Leave it to rise for about an hour.
Divide the dough into 4 parts. Roll them out with your hands to make sheets. Smear them with butter and crumble feta cheese on top.
Wrap them into rolls and place them in an oven dish, twisting them a bit.
Smear with the egg yolk. Wait for it to rise again. Bake in a moderate 340°F (170 °C) oven until golden.