Mix all the ingredients for the nut dough and stir until smooth. Then roll out the dough to a thickness of about three millimeters and cut out circles with a diameter of six centimeters.
Cut the marzipan bread into one centimeter thick slices. Place the cut-out nut cookies on a baking sheet, place one slice of the marzipan on each cookie and place another cookie on top. Gently press this top half smooth.
Bake the nut cookies at 180 °C for ten to fifteen minutes.
Mix the powdered sugar with water until you get a thick icing. When the cookies have cooled, the icing can be applied in streaks or blobs. Decorate immediately with a walnut half and drizzle again with a little bit of icing.