How to Make It
Preheat oven to 400°F. Make 1/2-inch cuts in duck fat about 1 inch apart in a diamond pattern. (Do not cut through flesh.) Sprinkle both sides of duck evenly with five spice and 1 1/2 teaspoons of the salt.
Heat a large heavy skillet or cast-iron skillet over high until very hot. Place duck breasts, skin-side down, in skillet, and reduce heat to medium-low. Cook until duck skin is deep golden, about 23 minutes, carefully discarding drippings halfway through cooking time.
Transfer breasts, skin side up, to a rimmed baking sheet. Bake in preheated oven to desired degree of doneness, about 8 minutes for medium.
Meanwhile, place skillet over medium-high; add wine, and bring to a simmer. Cook, stirring occasionally, until reduced by half, about 2 minutes. Whisk together cornstarch and orange juice; add to wine with remaining 1/2 teaspoon salt. Cook, whisking constantly, until thickened, about 1 minute. Add rice vinegar and orange zest; stir until smooth. Slice duck, and place on a platter with orange slices. Drizzle sauce over duck before serving; garnish with scallions. Serve with Lime-Scallion Pancakes.