Grate or grind 3/4 of the packet of Piskoty, and mix with the sugar, butter, cocoa and rum and milk. Roll the dough into small balls in the icing sugar and then put it in the wasps´ nest-shaped mold. Before taking it out of the mold, make a hole in the centre of the dough and fill it with the eggnog. Put a piskot lid on the bottom, so that the filling doesn´t leak out. It is best to leave them sit for a few hours before consuming them.