Wash the liver, dab dry and cut into pieces. Peel and chop onions, dice toast. Wash and quarter apples and remove the core. Cut apple quarters into thin pieces.
Fry the liver in hot oil for about 5 minutes while turning. Add onions, bread cubes and 2/3 of the apple pieces and fry briefly. Season with salt, pepper and marjoram. Drizzle the remaining apple pieces with lemon juice.
Wash the duck and pat dry. Rub inside and outside with salt and pepper. Add apple-liver-farce and tie up with kitchen string and wooden skewers. Tie wings and thighs. Place the duck on a fat pan rinsed with cold water and roast in a preheated oven (electric cooker: 200 °C/ gas: level 3) for about 1 1/4 hours.
Peel and wash the potatoes and cook them in boiling salted water for about 20 minutes. Clean, wash and possibly halve the Brussels sprouts. Sauté in hot fat, pour on 1/8 litre stock and cook for about 25 minutes.
Add the remaining apples shortly before the end of the cooking time. Season with salt and pepper. Drain the potatoes. Wash parsley, dab dry, chop finely and sprinkle over the potatoes. Remove the duck from the fat pan.
Pour frying stock through a sieve, degrease and fill up to 300 ml with the remaining stock. Add cream and bring to the boil. Stir in sauce thickener. Season to taste with salt and pepper. Arrange duck and vegetables on a plate.
Sprinkle with fresh marjoram. Sauce and parsley potatoes extra rich.