Score the duck breasts in a crosshatch pattern without cutting into the meat. Season them with pepper, salt, and marjoram.
Remove the skin from the onion. Halve it and then chop it into small pieces.
Sear the duck breasts on the scored fat side for 5 minutes. Flip them over and sear for another minute, then let them rest.
Meanwhile, sauté the onion in the same pan.
After two minutes, add the port, red wine, and poultry broth to the pan, along with the marmalade and cranberries. Let this simmer gently.
In another pan, caramelize the brown sugar. Deglaze with the orange juice.
Allow the sugar to melt completely again and then add the mixture to the cranberries.
Transfer the cranberries with the sauce into the roasting pan. Add the cinnamon sticks and star anise.
Place the duck breasts, with the seared fat side up, into the cranberry sauce.
Let everything cook in an oven at 80°C for 45 minutes.