For the dough, quickly knead together 100 g cold butter, flour, 100 g ground hazelnuts, 100 g sugar, salt and egg. Wrap the dough in foil and leave to cool for 30 minutes.
Preheat stove to 175 °C. Line 2 baking sheets with parchment paper. Roll out the dough on the lightly floured surface to a thickness of approx. 0.5 cm and cut out approx. 50 round cookies (diameter approx. 3.5 cm). Place on baking sheets and bake for about 10 minutes each. Cool.
Roast 75 g ground nuts without adding fat, cool. Mix with 100 g butter, 100 g sugar and rum to a smooth cream. Place in a piping bag with a nozzle and pipe onto half of the cookies. Place remaining cookies on top.
Warm jam, 1 small blob on each cookie mold. Place the hazelnut kernels on top. Dust with powdered sugar if desired.
Baking time. Approx.50 min – Cool for about half an hour – Bake for about 20 min.