Whip the egg whites with sugar until stiff peaks form, then gradually add the egg yolks. Finally, gently fold in the cocoa powder with the baking soda. Pour the batter onto a baking sheet lined with parchment paper. Bake at 180°C for approximately 8-10 minutes. After baking, turn it out onto a damp towel and roll it up.

To prepare the filling, mix the flour into the milk and cook a thick cream, then let it cool. Once the cream is lukewarm, beat in the softened butter and divide it into 2 parts. Add vanilla to one half, and cocoa powder and powdered sugar to the other. Once the cake has cooled, unroll it and remove the parchment paper. First, spread the light filling, then the dark filling, and roll it into a roulade. Let it chill in the refrigerator, preferably until the next day.