Cream butter, sugar, salt and vanilla sugar with the whisk of the hand mixer. Add lemon zest and juice and stir in. Mix flour, starch and baking powder and sieve onto the fat-sugar mixture. Knead with the dough hooks of the hand mixer to a smooth dough (dough is slightly softer). Chill for about 1 hour. Form approx. 80 balls (approx. 1.5 cm Ø) from the dough with floured hands. Place on three baking trays lined with baking paper (not too tight), press down lightly and bake in the preheated oven (electric oven: 150 °C/ gas: level 1) one after the other for 15-18 minutes.
Remove from the oven, carefully remove from the baking paper, place on a grid and allow to cool well. Spread half of the cookies (the undersides) with rosehip jam. Place one cookie on each side. Coarsely chop the chocolate coating, place in a bowl and melt in a hot water bath. Leave to cool a little. Pour into a small freezer bag and cut off a corner with sharp scissors. Decorate the cookies with the chocolate coating and let them dry