Beat eggs with sugar and vanilla sugar in a lush mass. Rub the cottage cheese through a sieve (in a blender) into a plastic mass without grains.
Add cottage cheese, sifted flour, starch, slaked vinegar, to the egg mass. Mix everything well. The test should not be very thick.
Heat vegetable oil in a pan with a thick bottom. Grease your hands with vegetable oil and pinch small pieces from the dough, form a cake on the palm of your hand and put a piece of chocolate (1cm * 1cm) in the center, roll a ball the size of a walnut. Make sure that there are no holes in the ball, otherwise chocolate may leak out of the donut at high temperature.
Carefully put future donuts in hot oil, there should be enough oil so that the balls do not touch the bottom of the pan.
Fry until golden brown. Hot donuts can be put on a paper towel to absorb excess fat.
Sprinkle the donuts with powdered sugar before serving.