Put 300 g flour, sugar, vanilla sugar, 1 pinch of salt, ##egg## and butter in flakes in a bowl. Knead first with the dough hooks of the hand mixer, then quickly with your hands to a smooth dough.
Wrap in foil and chill for about 1 hour.
Line three baking trays with baking paper. Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: level 3). Roll out the dough to a thin layer of flour about 2 mm thick. Cut out approx. 70 circles (approx. 5 cm Ø), knead and roll out the remaining dough again and again.
Place circles on the sheets. Bake in a hot oven for 7-9 minutes. Let it cool down.
Stir the jam and 2 tablespoons of rum until smooth. Spread half of the cookies with jam. Place the remaining biscuits on top.
Mix icing sugar, 4-5 tablespoons rum and ##lemon juice## to a smooth glaze. Spread the top of the cookies with it. Leave to dry.