Mix butter, 1 egg yolk, icing sugar and vanilla sugar with the whisk of the mixer. Sift the flour over it and knead it in
First form the dough into a roll (approx. 5 cm Ø), then press all sides flat enough to form a rectangular bar (approx. 3 x 6 cm). Leave to rest in the refrigerator for at least 3 hours, preferably overnight
Line two baking trays with baking paper. Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: level 2). Whisk 1 egg yolk. Brush the dough stick with it all around and roll in the sugar. Cut into approx. 1⁄2 cm thick slices and spread on the trays
Bake in a hot oven for about 10 minutes one after the other. Leave to cool on the trays. Store heather snow dry and cool in well sealed cookie tins
waiting time 3 hours