Beat whole eggs with a mixer, then add sugar and vanilla sugar.

Beat until foamy.

Pour milk and oil and mix briefly with a mixer.

Then add flour, cocoa and baking powder to the mixture and mix.

Line a 14x8 inches baking pan with baking paper and pour the resulting mixture.

Bake in a preheated oven for 30 minutes at 375 degrees Fahrenheit.

Before the end of baking, prepare the topping.

Pour milk, oil, sugar, cocoa and cooking chocolate into the cooking vessel.

Heat the mixture while stirring.

Let it boil, then remove it from the heat to cool down a bit.

Use a toothpick to check whether the biscuit is cooked, then take it out of the oven.

Remove the still hot sponge cake from the pan by turning it over, remove the baking paper, and then return the sponge cake back to the pan.

Pierce the biscuit in several places with a toothpick.

Cut it into cubes.

Pour the warm dressing evenly over the warm cake.

Cool everything well overnight and sprinkle with sliced walnuts before serving.