Put about 2/5 cup (100 ml) of the warm milk in a bowl, plus the yeast and 2 tbsp flour. Wait for it to activate and in the meantime beat the egg mixture.
Once it rises, divide it into 2 equal-sized parts and each of those into 3. Roll out each one into a small sheet and smear it thoroughly with butter. Put 3 sheets together and wrap them into a roll.
Cut the 2 resulting rolls into triangles. Arrange them in an oven dish. Form the middle with their vertices. After they rise, smear them with the beaten together egg yolk, milk and oil.
Bake in a preheated 320°F (160 °C) oven.