One 10-ounce Yukon Gold potato, peeled and cut into 1/3-inch dice
1 small shallot, minced
2 teaspoons capers, coarsely chopped
1/4 teaspoon chopped thyme leaves
3 tablespoons red wine vinegar
2 teaspoons Dijon mustard
Kosher salt and freshly ground pepper
1/2 large head of Napa cabbage, finely shredded (8 cups)
Preheat the broiler and set an oven rack 3 inches from the heat. Set the duck on a baking sheet and broil for 10 minutes, rotating the baking sheet, until the skin is crisp and browned all over.
Meanwhile, in a large skillet, heat the oil. Add the potato and cook over moderately high heat until golden, 8 minutes. Add the shallot and cook over moderately low heat for 1 minute. Add the capers and thyme and cook for 30 seconds. Stir in the red wine vinegar and mustard and season with salt and pepper.
Remove the meat and skin from the duck; discard the bones. Scrape away any fat that remains on the underside of the skin. Cut the skin into strips and shred the meat. In a bowl, toss the duck, cabbage and dressing. Season with salt and pepper and serve.