Roughly chop 250 g couverture and melt while stirring on a hot water bath. Let cool down lukewarm.
Mix the oil, sugar, vanilla sugar and salt for 8 minutes until creamy. Stir in eggs one at a time. Add yogurt and melted couverture. Mix flour with baking powder and stir in briefly. Smooth out the dough on a greased baking sheet. Bake in a preheated oven at 175 ° C top / bottom heat (convection 150 ° C) for about 50 minutes. Take out the cake and let it cool down!
Roughly chop 250 g couverture, also melt in a water bath, let cool for 10 minutes and spread on the cake. Let everything cool until the couverture is hard.