Activate the Yeast: In a large bowl, combine 200 ml of warm milk (make sure it’s not too hot, around 37°C/100°F) with 2 tablespoons of sugar and 7 g of instant yeast. Let the mixture sit for 5-10 minutes until bubbles form, indicating the yeast is active.

Mix the Dough: In the same bowl, add 1 egg, 3 tablespoons of vegetable oil, and ½ teaspoon of salt to the yeast mixture. Gradually add in the flour, starting with 450 g, and mix with a spoon or spatula. Once the dough starts coming together, switch to using your hands and knead the dough on a lightly floured surface. If the dough is too sticky, gradually add the remaining flour, kneading until you have a smooth, elastic dough. Knead for about 7-10 minutes.

Let the Dough Rise: Place the dough in a lightly oiled bowl, cover with a clean kitchen towel or plastic wrap, and let it rise in a warm place for about 1-1.5 hours or until it doubles in size.

Mix the Filling: In a medium-sized bowl, combine 400 g of cottage cheese, 1 egg yolk, 8 g of vanilla sugar, 1 tablespoon of cornstarch, 2 tablespoons of sour cream, 2 tablespoons of sugar, and a pinch of salt. Mix everything together until smooth and well combined. Set the filling aside.

Punch Down the Dough: Once the dough has risen, punch it down gently to release the air. Transfer it to a lightly floured surface and divide it into equal portions, around 12-15 pieces, depending on how large you want the buns to be.

Form the Buns: Roll each portion of dough into a ball, flatten slightly with your hand, and place them on a baking sheet lined with parchment paper. Make sure to leave some space between each bun as they will expand while rising.

Create the Wells: Using the back of a spoon or your fingers, press down in the center of each dough ball to create a well for the filling. Be careful not to press too hard, as you don’t want to make a hole through the dough. The well should be about 1-2 cm deep.

Fill the Buns: Spoon a generous amount of the prepared cottage cheese filling into each well, filling them to the brim.

Let the Buns Rise Again: Cover the buns loosely with a kitchen towel and let them rise for another 20-30 minutes while you preheat the oven to 180°C (350°F).

Prepare the Egg Wash: In a small bowl, whisk together 1 egg and 1 tablespoon of milk. Brush the tops and edges of the dough with the egg wash. This will give the buns a beautiful golden color when baked.

Bake: Place the baking sheet in the preheated oven and bake for 20-25 minutes, or until the vatrushki are golden brown and the edges are firm.

Cool and Dust with Powdered Sugar: Once the buns are baked, remove them from the oven and let them cool on a wire rack. If desired, dust the vatrushki with powdered sugar before serving for an extra touch of sweetness.