Cook the lentils in boiling water for about 40 minutes. Peel, wash and finely dice carrots. Cook briefly for the last 5 minutes.
Chop the plums finely. Peel and chop the onions. Wash duck skin, dab dry and cut into strips or cubes. Fry until crispy in a hot pan. Season with salt and drain on kitchen paper.
Drain duck fat to approx. 2⁄3 Fry onions in the rest. Deglaze with vinegar. Season with salt, pepper and sugar.
Lentils and carrots quench and drain. Mix with plums and marinade. Leave to soak for at least 2 hours. Flavour again and serve. Wash the chives, dab dry and chop finely.
Sprinkle lentil salad with chives and crispy duck skin.