01 -
Preheat oven to 180°C. Line a 30 by 40 cm baking tray with parchment paper.
02 -
In a large mixing bowl, beat egg whites with a pinch of salt until soft peaks form.
03 -
Gradually add sugar and continue beating egg whites until stiff peaks are achieved. Gently fold in the cooled, melted chocolate to avoid deflating the mixture.
04 -
Sift wheat flour and baking powder into the chocolate egg white mixture. Fold in gently until just combined.
05 -
Pour the batter into the prepared tray and spread evenly. Bake for 8 minutes or until a toothpick inserted in the centre comes out clean.
06 -
Allow the cake to cool completely in the tray. Carefully remove from parchment paper.
07 -
Whisk egg yolks, sugar, and cornstarch together in a bowl until smooth. Heat milk in a saucepan over medium heat until warm, then gradually whisk into the egg mixture to temper.
08 -
Return the mixture to the saucepan and cook over medium heat, stirring constantly, until the custard thickens. Remove from heat and stir in vanilla sugar and butter until smooth and glossy. Cool to room temperature.
09 -
Slice the cooled sponge horizontally into two even layers. Place the first layer on a serving tray and brush lightly with half the milk for soaking.
10 -
Spread half of the cooled custard evenly over the soaked sponge layer.
11 -
Place the second sponge layer on top, soak with the remaining milk, and smooth the remaining custard over the top.
12 -
Heat milk and butter in a small saucepan over low heat until butter melts. Add chopped chocolate and stir gently until fully melted and smooth. Allow glaze to cool slightly.
13 -
Pour the warm glaze over the top custard layer and spread evenly with a spatula.
14 -
Refrigerate for at least 2 hours to set. Slice into squares before serving.