Bring a large pot of salted water to a boil. Add potatoes; cook just until tender. Drain well.
Meanwhile, combine mayonnaise, spinach leaves and fresh herbs in a small food processor. Process until smooth.
Combine warm cooked potatoes, mayonnaise mixture, red onion, vinegar, sour cream, sugar, apple and salt and pepper to taste. Chill before serving. If desired, garnish with thinly sliced carrots or chives.