Mix butter, 50 g icing sugar, vanillin sugar, half lemon zest and 1 pinch of salt until creamy. Stir in the egg. Briefly stir in flour in portions. If necessary, stir in 1-2 tbsp. cold water.
Pour the dough into a piping bag with a star-shaped spout (11 mm Ø). Spray approx. 25 flowers onto baking trays covered with baking paper: with stems (4 cm long) and flowers on them as tuffs (3 cm Ø).
Bake in the preheated oven (electric oven: 200°C/circulating air: 175°C/gas: level 3) for about 10 minutes. Let them cool down.
Mix 125 g icing sugar and lemon juice. Spread the biscuits with it, decorate with pistachios and the rest of the lemon peel. Leave to dry.