Slightly heat the mixed together yoghurt and milk in a pot, dissolve the yeast in them, pour the mixture into a large, deep bowl.
Mixture must become smooth and thick. Put it in a warm area, covered with plastic wrap, for about 40 min. Heat the saj or pan on moderate stove, smear with a little butter, pour ladles of mixture in it.
After cooking the crepe to desired crisp, flip over and cook that side as well. Arrange the crepes on top of one another, smearing with butter slightly between them.