Melt the chocolate over a hot water bath. Stir in the butter and let cool. Separate the eggs. Beat the egg yolks and sugar until creamy. Stir in the chocolate. Beat the egg whites and 1 pinch of salt until very stiff. Fold the flour into the egg yolk mixture. Fold in the egg whites. Pour into a lined springform pan.
Bake for 25-30 minutes at 175ºC (approximately 350°F). Let cool in the pan. Whip the cream, vanilla sugar and the stabilizer until stiff. Spread on the cake. Cut into pieces and serve.