Melt butter in a saucepan and place in a mixing bowl. Add sugar, vanilla sugar, cocoa powder and salt and mix everything together. Gradually stir in eggs and water. Sift flour and baking powder onto the dough and fold in. Pour the dough into a mold (approx. 30 cm x 30 cm) that has been greased or lined with baking paper.
Bake in a preheated oven at 150 ° C for about 30 minutes.
Then sprinkle with powdered sugar as desired and cut into pieces.