Fluffy Berry Vatrushki with Crunchy Streusel

In a large mixing bowl, combine kefir and fresh yeast. Stir gently until the yeast dissolves completely.

Add the sugar, flour, salt, egg yolks, and vegetable oil. Mix everything together until a rough dough forms.

Knead the dough on a floured surface for about 10 minutes, or until it becomes smooth and elastic. Place it in a lightly greased bowl, cover with a towel, and let it rise in a warm place for about 1 hour.

While the dough is rising, make the filling. In a bowl, combine the cottage cheese, egg white, sugar, and vanilla sugar. Mix until smooth and creamy.

Set aside until the dough has finished rising.

In a small bowl, mix the flour, sugar, and butter. Use your fingers to work the butter into the dry ingredients until crumbly.

Set aside for later use.

Preheat your oven to 180°C (350°F). Once the dough has risen, punch it down and divide it into 8 equal pieces.

Shape each piece into a small ball and then flatten it into a disc. Create a small well in the center of each disc and fill it with the cottage cheese mixture.

Once filled, sprinkle some berries on top and then sprinkle the streusel topping over the berries.

Place the prepared vatrushki on a baking sheet lined with parchment paper. Brush the edges with egg white for a golden finish.

Bake in the oven for about 20-25 minutes, or until they are lightly golden brown on top.

Allow to cool slightly before serving warm. Enjoy your delicious and fluffy berry vatrushki!