1. Preheat oven to 400 degrees Fahrenheit.
2. With a sharp knife, score fat on duck breasts in a crisscross pattern.
3. Sprinkle duck with salt and pepper.
4. Place duck fat-side down in a cold cast-iron skillet. Cook over medium heat for six to eight minutes, until fat is rendered and crispy. Turn the duck breast over and sear for an additional two minutes.
5. Turn the fat side down and transfer skillet to the oven to roast for six to eight minutes, until breasts are medium rare. Remove from the oven and let rest for five minutes before slicing.
6. While the duck breasts are in the oven, make the sauce. Combine sugar and water in a pan. Cook over medium heat until the sugar melts and caramelizes, about one minute. Add wine, vinegar, stock, and orange juice. Bring to a boil.
7. Add pan drippings from the seared duck breasts. Mix well and simmer over medium heat, until reduced by half. Season with salt and pepper.
8. To assemble: Sauce goes on the bottom, a slice of duck on top, and the segmented orange slice is for garnish.