Preheat the oven to 180°C (356°F) and line a 30 x 20 cm baking sheet with parchment paper.

Beat the egg whites in a mixing bowl until stiff peaks form.

Beat 150 g butter with 150 g granulated sugar until pale and fluffy.

Sift 70 g all-purpose flour into the butter mixture and add 150 g ground walnut.

Fold the flour and walnut into the butter mixture with a rubber spatula.

Gently fold the beaten egg white into the batter until no white streaks remain.

Spread the batter evenly in the lined baking sheet and bake for 20 to 30 minutes.

Remove the biscuit when its edges are golden brown and keep it in the baking sheet.

Beat 4 egg yolks with 150 g powdered sugar and 10 g vanilla sugar until smooth.

Pour the yolk cream evenly over the hot baked biscuit.

Turn off the oven and leave the cake inside for 30 minutes to dry the yolk cream.

Bring 100 ml milk and 100 g granulated sugar to a brief boil in a saucepan.

Remove the saucepan from the heat and add 100 g butter with 100 g dark chocolate.

Stir the chocolate mixture until melted and completely smooth.

Stir 100 g ground walnut into the chocolate cream.

Pour the chocolate cream over the dried yolk layer and spread it evenly.

Refrigerate the cake overnight until the chocolate layer is firm.

Sprinkle the cake with walnut and cut it into crescent shapes before serving.