Cut the butter into cubes and set aside. Prepare the dough. Pour warm water into a bowl and add yeast and 1/2 teaspoon of white sugar. Set aside for 5 minutes to allow the yeast to dissolve in the water. Then pour 1/3 cup flour into a bowl and stir until smooth. Cover the dough and place it in a warm place to rise for 30 minutes. Heat the milk in a small saucepan over low heat. Pour some salt and 1/4 cup sugar into a saucepan. Remove the saucepan from the stove and let it stand for 2-3 minutes at room temperature.
Pour milk from a saucepan into a large bowl, add vanilla extract, vanilla seeds, and eggs, mix well. Add the dough to this mixture and gradually add the remaining flour (3/4 cup at a time). Then add softened butter. Knead a homogeneous dough. Cover the bowl with the dough and place it in a warm place to rise for about 2 hours (the dough should double in volume).
Cover two medium-sized baking sheets with parchment. Put the dough from a bowl on a cutting surface, knead well and divide into two parts. Roll each part into an oval about 20×23 cm in size. Place the blanks on baking sheets, cover, and put in a warm place for an hour. Turn on the oven to preheat to 190 degrees.
Prepare the icing. In a bowl, combine melted butter and vanilla extract. Grease the dough that has come up with icing and sprinkle with unrefined sugar. Place the baking sheets in a preheated oven and bake sweet bread for about 25 minutes, until golden brown.