For the Sachertorte preheat oven to 190°C. Melt the semisweet chocolate in a water bath while stirring. Allow to cool. Mix the butter, icing sugar, vanilla sugar and salt. Mix until frothy and add the yolks one after the other. Beat the egg whites with the sugar until firm, sift the flour. Carefully fold in the egg white and flour alternatively into the chocolate mixture. Grease the cake pan with butter and dust with flour. Fill in the mass and bake in the oven for approximately 60 minutes. Sprinkle granulated sugar on the baking paper, turn out the cake onto it and allow to cool.
Cut the cake horizontally into two layers and coat with half of the jam, put together again. Heat the remaining jam and spread thinly all over the cake. Warm the chocolate icing according to instructions and ice the cake.
It is best to prepare the cake on the previous day and to keep in the refrigerator overnight. Sachertorte is traditionally served with whipping cream.