Sort the blackberries, wash and drain them if necessary. Put 2 paper sleeves in each. Distribute on a baking tray. Preheat oven (electric cooker: 200°C/circulating air: 175°C/gas: level 3).
Mix flour, baking powder and baking soda. Whisk the egg in a large mixing bowl and stir in 75 g sugar, vanillin sugar, oil and quark. Add the flour mixture and stir in very briefly with a wooden spoon until everything is mixed.
Carefully fold in the blackberries.
Spread the dough into the paper sleeves using a teaspoon. Bake in a hot oven on the middle shelf for 18-20 minutes. Let it cool down.
Stir the sauce powder, 2 tablespoons of sugar and 6-7 tablespoons of milk until smooth. Boil up the remaining milk and cream. Stir in the sauce powder and bring to the boil again while stirring. Dust muffins with icing sugar. Serve the sauce lukewarm or cold with the muffins.
If some muffins are left over, wrap them in aluminium foil and freeze them.