Preheat the oven to 180 ° C. In a small bowl, beat the cream cheese with sugar and vanilla sugar until frothy. Mix the flour, baking powder, baking soda and cocoa powder well in another bowl. Lightly whisk the egg in a large bowl. Add the brown sugar, oil and buttermilk and stir. Carefully fold in the flour mixture.
Pour quarters of the batter into the wells. Put 1 teaspoon filling on each and fill with batter. Bake in the middle shelf at 160 ° C fan oven for 20-25 minutes. Let cool down. Dip in couverture, let it dry a little and sprinkle with chocolate sprinkles.