Chop the ginger finely. Separate egg. Mix flour, starch, sugar, vanilla sugar and 1 pinch of salt. Add butter in pieces, egg yolk and 2 tablespoons of cold water to the flour mixture. Knead everything first with a hand mixer and then briefly with your hands until smooth.
Form the dough into a roll (approx. 28 cm long). Whisk the egg white and spread a thin layer on the roll. Turn in the ginger, pressing the ginger down well. Place in the freezer for about 10 minutes.
Line a baking tray with baking paper. Cut the roll of dough into approx. 30 slices (just under 1 cm thick) and place on the baking tray. Bake in the preheated oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2) on the middle shelf for about 18 minutes.
Let it cool down.