Onions peel, 1 quarter. Wash the legs. Bring to the boil with onion quarters, peppercorns, bay leaf and salt covered with hot water. Cover and cook for 40-45 minutes.
Soup greens clean or peel, wash and cut into strips. Dice 1 onion. Fry in 2 tbsp. hot oil. Rinse the lentils. Add half of the soup greens and fry. Deglaze with 3/4 l water. Bring to the boil and stir in stock. Cover and cook over medium heat for about 45 minutes. After approx. 30 minutes add the rest of the soup vegetables and approx. 1/8 l duck stock, finish cooking
Wash the duck breast. Remove the legs from the broth. Dab all duck parts dry and season with salt and pepper. Bake in a preheated oven (electric cooker: 200 °C / convection oven: 175 °C / gas: level 3) on an oiled fat pan for about 45 minutes until crispy
Wash the parsley and chop it except for one thing. Season lentils with salt, pepper, sugar and mustard. Refine with crème fraîche. Arrange the duck pieces on top. Sprinkle with parsley and garnish. Serve with boiled potatoes