Wash the turkey leg, dab dry and season with salt, pepper and marjoram. Peel and quarter the onion. Put turkey leg, onion and oil in a large roasting pan. Roast in the preheated oven (electric cooker: 175 °C/ gas: level 2) for about 2 hours.
Pour on chicken soup after about 40 minutes. Clean, wash and drain the soup greens. Cut carrots and leek into slices, celery into cubes. Peel, wash and quarter potatoes lengthwise. Distribute potatoes and vegetables around the leg about 50 minutes before the end of the frying time and season with salt and pepper.
Add bay leaf and braise while stirring occasionally. Heat up the jam and spread on the leg about 15 minutes before the end of the cooking time. Wash parsley, dab dry and chop except for a little bit for garnishing.
Serve the meat and vegetables sprinkled with parsley and garnished.