Warm the milk and dissolve a teaspoon of sugar in it. Crumble the fresh yeast into the milk and let it sit for 5 to 10 minutes until frothy.

In a mixing bowl, combine flour, remaining sugar, and a pinch of salt. Make a well in the center, then add the yeast mixture, egg, and melted butter. Knead for 8 to 10 minutes until smooth.

Place the dough in an oiled bowl, cover with a cloth, and let it rise for about 1 hour, or until doubled in size.

In a separate bowl, mix cottage cheese, sugar, egg yolk, lemon zest, vanilla extract, and optional raisins until well combined. Add sour cream if needed for consistency.

Preheat oven to 180 degrees Celsius (350 degrees Fahrenheit). Line a baking sheet with parchment paper.

Once the dough has risen, roll it out into a rectangle about 3 to 4 mm thick. Cut into squares of about 10 by 10 centimeters.

Place a spoonful of filling in the center of each square, gather corners to the center, and press lightly to seal.

Arrange the pastries on the baking sheet, allowing space between them. Cover and let rise for another 20 to 30 minutes.

Mix egg yolk and milk for the egg wash, then brush over the tops of the pastries.

Bake for 20 to 25 minutes until golden brown. Cool on a wire rack.