For the filling, stir the cream cheese with sugar and vanilla sugar in a small bowl.
In another bowl, carefully mix the sifted flour, baking powder, baking soda and cocoa powder.
Beat the egg in a large bowl and whisk gently. Add the brown sugar, oil and buttermilk and mix well. Then carefully fold in the flour mixture.
Distribute a quarter of the dough in the baking tray. Then put 1 teaspoon of filling on each and fill up with batter.
Bake in the oven at 160 ° C (convection) for about 20-25 minutes.
Take the muffins out of the baking sheet and place on a wire rack to cool.
Melt the couverture in a saucepan in a water bath while stirring. Dip the muffins in the couverture and let them dry a little, then sprinkle with the chocolate sprinkles.