For the dressing: In a bowl, stir together the sugar, curry powder, and vinegar. Add in the sour cream, and mix to combine. For the slaw: Put the Napa cabbage in a bowl, and season with salt, to taste. Toss the cabbage with the red onion, carrot, pear and parsley to incorporate. Pour the dressing over the slaw just before serving, and toss to combine. Transfer the slaw to a serving bowl.