Wash the carrots and peel them if necessary. Core the apples (do not peel). Grate both finely on a grater (or in a food processor) and place in a large bowl.
Peel and finely dice the onion. Peel the mandarins and cut into small pieces. Add both to the carrots and apples.
Prepare a salad dressing from the yogurt, oil, lemon juice, honey, salt, pepper, cayenne pepper and garlic powder and season well.
Add the sauce to the carrots and mix everything well. Stir in the chives and let everything stand for about 1 hour at room temperature.
Season the salad again before serving and sprinkle with the chopped walnuts.