For the shortbread, preheat oven to 160°C hot air. Beat butter, sugar and vanilla sugar until fluffy. Mix flour and baking powder with the egg mixture.
Fill the dough into a piping bag and pipe about 3 cm long bars onto a baking tray lined with baking paper.
Bake in the oven for 10-15 minutes. The bars should not turn brown. Melt the chocolate, dip the cold piped pastry and let cool on a baking paper.