Carefully remove the skin of the duck breast from the meat with a kitchen knife and cut into 1_cm wide strips. Fry in a frying pan until crispy, remove from the fat with a skimmer and drain on kitchen roll. Keep the fat.
Clean the spring onions and cut them into thin rings. Roast the chanterelles in the duck fat until the liquid has evaporated, then add the onions and spring onions and briefly sauté until translucent. Season with salt and pepper and set aside.
In the meantime, cook the washed potatoes in salted water, drain and cool a little.
For the salad dressing, stir chicken stock with white wine vinegar, mustard and oil and let it boil once. Peel the potatoes and cut them into slices into the warm salad dressing. Add the mushrooms and onions and mix carefully with the potatoes. Cut the arugula into thin strips and add to the lettuce. Season everything with salt and pepper. Cover the salad with a lid and let it stand for at least thirty minutes, keeping it warm.
For the duck fillets, heat the oil in a frying pan. Season the duck meat with salt and pepper and roast in the oil over medium heat for about five to seven min on each side, then wrap tightly in foil and keep warm.
Extinguish the drippings with remaining chicken stock and boil until reduced by half. Season with balsamic vinegar, salt, pepper and sugar.