Beat the egg whites until fluffy, gradually adding the sugar and mixing until homogeneous. Combine the whites beaten with sugar with the yolks. In a separate bowl, sift the cake flour, potato flour and baking powder, and add it, while mixing gently, to the beaten mixture combined with the yolks. Transfer the cake batter to a baking tin and bake at 170°C (thermo) or 180°C (no thermo) for 30-40 minutes until golden. Leave the baked sponge cake to cool, remove from the tray and divide into four equal tops.

Melt the chocolate by stirring in a water bath, not exceeding 80°C. Let the melted chocolate cool down to 30-32°C, but allow it to remain liquid and not yet start to crystallise. Whip the cooled cream until stiff. Gradually, while stirring, add the melted, cooled chocolate and stir until it combines with the cream to form a homogeneous mass. Set aside in the fridge and use to layer the middle layer of the cake.

Heat the halva cream in a water bath or in a hothouse to approx. 45°C, until slightly melted. Whip the cream and slowly add the custard, stirring continuously until homogeneous.

Bring the cream to the boil and add the chocolate, stirring until the chocolate is melted. Add butter and mix thoroughly. Let cool but do not allow it to solidify.