Prepare the dough. Pour 0.5 cup warm milk in a bowl, add 1.5 tsp. yeast and stir with a mixer until yeast dissolves. Add 1 egg, 1 tbsp. sugar, a pinch of salt, stir and gradually pour in flour. Make slack dough during 6 - 8 minutes. If the flour absorbs more liquid and the dough is not soft, you can add 1 - 2 tbsp. milk. At the end of kneading, add a slightly warmed margarine and mix thoroughly. Put the ready dough on the table and crumple slightly by hand giving the shape of a ball. After that, put the dough in a bowl, cover with a film and leave in a warm place for 1.5 - 2 hours for fermentation. When the dough volume doubles, punch it, put back in a bowl, cover with a film and leave for another 40 - 50 minutes. Upon this lapse of time, slightly grease the table and hands with vegetable oil, put the dough on the table and crumble it. Roll the dough into a bundle and cut into 10 nearly equal pieces. Make balls out of them and, slightly flattening, lay out on a greased baking sheet at a distance of at least 5 centimeters from each other. Leave to prove for 5-10 minutes. Prepare the filling while the dough is being proofed. Rub 1 cup of cottage cheese through a sieve, add 1 egg, stir, add 1.5 tbsp. sugar, a pinch of salt, 1 tsp. vanilla sugar and 1 tsp. flour. Mix everything thoroughly - the filling is ready. Make grooves in the dough with the bottom of a glass and fill them with stuffing. Since everyone likes more cottage cheese to be in vatrushka, it is advisable to make a double portion of the filling and make the grooves with a large glass. Cover vatrushkas with a towel and leave to proof for 20 - 25 minutes. In 20 - 25 minutes, brush the surface of vatrushkas with a beaten egg yolk and place them in the oven. Bake at 200°C for 12-15 minutes. Lay the baked vatrushkas out on a grate and let them cool.