Mix the butter and icing sugar until foamy. Blend with the eggs, salt and vanilla sugar. Mix the flour with a wooden spetula through the sugar mixture.

Pour the dough into a piping bag with a smooth nozzle of 1 cm diameter. Squirt small bars of 6 cm on a lightly greased baking tray. Be sure to leave some space between the bars since the flow during baking. Bake for 8-10 minutes in an oven of 170ºC. The edges should be brown, the middle golden/yellow.