Instructions

1. Whip the butter, icing sugar and vanilla until creamy in a large bowl.
2. Add the egg yolks slowly and continue beating until the mixture is thick.
3. Melt the chocolate in a double boiler. When completely melted, fold into the mass.
4. Beat the egg white until stiff, sprinkling in the sugar and continue to beat until the mass is glossy and stiff.
5. Stir and heap the beaten egg white onto the egg yolk mixture, sift in the flour and carefully fold with a large spoon.
6. Line the bottom of the spring form with baking/parchment paper and grease the sides of the form with butter.
7. Sift over some flour.
8. Fill the spring form with the mixture and spread evenly.
9. Bake in a preheated oven at 340F °C for 55–60 minutes, leaving the door slightly ajar during the first 10–15 minutes.
10. Turn the cake upside down on a cake rack and allow to cool for about 20 minutes. Open up the spring form and peel off the paper.
11. Put the form back on the cake, then turn the cake over. Allow to fully cool