Add sugar to the eggs and beat with a mixer at maximum speed until thick and fluffy.
Add flour to the egg mixture and stir. Then add milk and stir until smooth. Then add cocoa and vanilla sugar and stir.
Pour the resulting dough into a baking pan and put it in the oven. Bake until done. Do not open the oven for the first 15 minutes to avoid cooling the air. After 25-30 minutes, check the readiness of the sponge cake with a toothpick. Pierce the cake with a toothpick, there should be no dough left on it.
Prepare the cream. Add sugar to the sour cream and beat thoroughly. Add yogurt. In a separate bowl, beat the cream and mix with the sour cream mixture.
Cool the finished cake and cut the cake lengthwise into 3 parts. Spread the prepared cream on the cakes and assemble the cake. Leave it in the refrigerator for a few hours so that the cakes soak and the cream thickens.