Melt the chocolate. Mix the butter with sugar, vanilla sugar and milk until frothy, add the melted chocolate and eggs and mix everything well. Chop the walnuts and stir in with the oatmeal. Mix the flour with baking powder and salt and stir in as well.
Spread the dough on a deeply greased or parchment-lined baking sheet and bake at 150 ° C for 30 minutes.
Cover with chocolate icing if you like. Cut into approx. 20 cuboids.