Pour warm milk (38-40 °C) into a large bowl, put yeast and stir. Gradually pour in part of the sifted flour and knead sponge dough: its consistency should be like that of a liquid sour cream. Leave the sponge dough covered with a towel in a warm place for 40 minutes. Add softened butter, sugar and salt to the sponge dough. Stir until sugar and salt completely dissolve. Add the sifted remaining flour in small portions, thoroughly mixing each time. Knead dough, cover and put in a warm place to rise for 1.5 hours. After the dough rises, make it soft by mashing. Then set aside for another 1.5-2 hours. For the filling, finely chop the cabbage to form short, thin pieces. Put the cabbage in a large saucepan, add salt, stir and top with cream. Cover and simmer, often stirring, for about 20 minutes until the cabbage is soft. For 5 minutes before done, add 1-2 tbsp. butter. Boil eggs hard, peel and chop not too finely. Mix the eggs and the ready cabbage, and salt. Roll out 2/3 of the dough into a layer to be slightly larger than your baking tray. Lay the cabbage filling in an even layer and wrap the hanging edges over the filling. Roll out the remaining dough, cover the filling and pinch the edges. Make a few holes for the steam outflow, brush the dough with a yolk -water mixture and leave for 15 minutes. Bake at 180 °C for about 1 hour. When the pie is baked, you can grease it with butter and let it cool under a towel.