Pour the flour into a bowl with the yeast. Stir to mix both. In another bowl, break 2 eggs. Stir them with a whisk or fork.
Add 3 tbsp butter, 1 pinch salt, 1 pinch sugar. Stir and add the yoghurt and sour cream. Stir and add to the flour. Crumble the feta cheese and add it as well.
Knead the dough in a bowl without taking it out. Cover it and leave it to rise for 40 min. Take it out of the bowl and form it into a ball by kneading. To prevent it from sticking, sprinkle the work area with flour.
Divide it into 9 equal parts. In a small bowl, soften 4 tbsp butter in the microwave. Put baking paper in an oven dish and arrange the salty balls, which you've formed well with buttered hands, in 3 rows.
Smear the top with 1/2 yolk (that's how many I had and they were enough) mixed with 2 tbsp oil using a brush. If desired, sprinkle with sesame seeds. Bake at 392°F (200 °C) in a preheated oven. What you get is really fluffy and aromatic Feta Cheese Buns.