For the dough, stir the butter with the sugar until frothy. Stir in the egg and the spices. Add flour, hazelnuts and breadcrumbs or biscuit crumbs and knead everything into a smooth dough. Cover and leave to rest in the refrigerator for an hour.
Roll out the dough on a floured work surface into a sheet about 5 mm thick and cut into small rectangles. Make small hollows in the middle with your thumb and add some jam. Place on a baking sheet and bake in the preheated oven on the middle rack for 15-17 minutes (electric stove: 190 °, gas stove level 2-3).
Let the pastries cool down on the wire rack.
For the icing, mix the sifted powdered sugar with the lemon juice and brush the biscuits with it.