For the walnut-marzipan cookies, first heap flour, walnuts and powdered sugar on the surface, put the egg yolks in the middle, put the chopped butter all around. Chop everything with a kitchen knife, then mix with your hands to form a smooth dough. Wrap in plastic wrap and refrigerate for 1 hour.
Roll out the dough on a floured surface to a thickness of two to three mm. Keep dusting the rolling pin with flour in between, as the dough sticks very easily. Cut out round cookies with a diameter of about three cm.
Place on a greased or parchment paper-lined baking sheet and bake in a heated oven at 180 °C for about 12 minutes.
In the meantime, knead the marzipan paste with 75 g of powdered sugar and roll out to a thickness of 2 mm on the remaining powdered sugar. Cut out round cookies with the same cookie cutter as for the dough.
Spread apricot jam on the cooled cookies, place a marzipan sheet on top and press smooth. Melt the cooking chocolate in a water bath, but in any case do not let it get too hot. Coat the walnut-marzipan cookies with the cooking chocolate and decorate with a walnut half.