Preheat the oven to 180°C (356°F) and line one baking tray.

Separate 7 eggs, then beat the egg whites to stiff peaks.

Beat the egg yolks with 200 g granulated sugar until pale.

Mix in 120 g dark baking chocolate, 150 g ground almonds, and baking powder.

Fold the whipped egg whites gently into the batter.

Roll out 1 puff pastry sheet to the baking-tray size on a floured surface.

Pour the batter over the pastry, then bake for about 25 minutes.

Whisk 30 g flour and 32 g cornstarch with a little of the 700 ml milk until smooth.

Bring the remaining milk to a boil, then whisk in the starch mixture until thickened.

Stir in 5 ml vanilla extract, then cover the custard surface and cool completely.

Roll out the second puff pastry sheet, then prick it all over with a fork.

Bake the second pastry sheet at 220°C (428°F) for about 10 minutes.

Beat 250 g softened butter with 250 g powdered sugar until fluffy.

Beat the cooled custard until smooth, then mix in the butter mixture.

Spread the cream over the baked cake layer, then place the crisp pastry sheet on top.

Dust the finished cake with additional powdered sugar before slicing.