Cut the marzipan into cubes and mix with half of the butter and powdered sugar until smooth. The marzipan should be fully dissolved. Add the remaining butter, orange zest, and egg yolks, mixing well. Finally, sift in the flour and fold it in. Grease and flour a baking tray. Preheat oven to 190 °C (375 °F). Fill a piping bag with the batter and pipe strips about 5–6 cm long onto the tray, like ladyfingers, leaving enough space as the batter will spread. Bake the orange fingers in the middle of the oven for 10 minutes and carefully remove while still hot. Put the orange marmalade into a paper bag and brush the underside of each finger, then sandwich two together with the marmalade sides inside. Melt the couverture chocolate and dip half of each orange finger. Scrape off excess and let them set on parchment paper.