In a salad bowl, pour the yogurt, flour, pinch of salt, eggs, and mix, then add the sugar, oil, yeast, and vanilla sugar. Mix again.
In a second bowl, pour the melted chocolate (in the microwave or in a bain-marie). Then in this chocolate paste, incorporate half of the white paste and mix!
Butter a mold, then pour a layer of the white dough, a layer of the chocolate, and so on.
Then take a knife and make marbling. Bake for about 40 to 45 min in a preheated oven at th.6 (180°C).