Preheat the oven to 180 °C (350 °F).
Thoroughly clean the ducks, then pat dry with paper towel. Trim excess skin from the ends, then place in large, high-rimmed roasting pan. Generously season with salt, pepper and Chinese five-spice and set aside.
Place the ducks in the oven, loosely cover with a sheet of aluminum foil and cook for 3 hours.
After 2 hours of cooking, remove from the oven and slather the ducks with half of the sweet chili sauce. Return to the oven and continue cooking, uncovered.
Brown the ducks at the end of cooking by turning on the broiler.
Remove the ducks from the oven and let stand for 15 minutes, loosely covered in a sheet of aluminum foil, before cutting into pieces. Brush the pieces with the rest of the sweet chili sauce and generously sprinkle with sesame seeds.
Serve with sautéed baby bok choy and white rice.
