Thoroughly rub fine fluff from the quince shells. Coarsely slice the quinces (see tip), peel, core and cut into pieces. Sprinkle with lemon juice. Caramelise the sugar in a pot until golden.
Melt 1 tablespoon of butter in it. Add apple juice and simmer while stirring until the caramel has dissolved. Add quince pieces and simmer covered for about 30 minutes.
Wash potatoes thoroughly and boil with skin in water for about 20 minutes.
Wash duck breasts, pat dry and cut the skin crosswise. Heat a flat roasting pan or an ovenproof pan without fat. Sauté duck breasts only on the skin side for approx. 4 minutes.
Turn and fry on the meat side for 2 minutes. Season with salt and pepper. Bake in a preheated oven (electric cooker: 200 °C/Um
Drain the potatoes and let them evaporate briefly. Fry in 2 tablespoons of hot butter while turning for about 10 minutes. Season with salt and pepper.
Wash the marjoram, shake dry and chop. Remove duck breasts from the oven, wrap in foil and leave to rest for about 10 minutes.
Degrease the roast and add the quinces with the juice and marjoram. Bring to the boil once. Season with salt and pepper. Cut the duck breasts into slices. Pour the resulting gravy into the quinces. Serve everything.