Remove excess fat from the duck breasts and pat dry with paper towels. Score the skin lightly in a criss-cross pattern without cutting into the meat. Season both sides with salt and black pepper.
Preheat the oven to 200°C (400°F / Gas 6).
Place the duck breasts skin-side down in a cold pan. Turn the heat to low-medium and allow the fat to slowly render out. Cook for 6–8 minutes until the skin becomes crispy and golden.
Flip and cook the other side for 1 minute to seal the meat.
Transfer the duck (skin-side down) to an oven-safe pan or baking tray. Roast for 6–10 minutes depending on your preferred doneness (5–6 minutes for medium, 8–10 for well done). Flip halfway through.
While the duck roasts, mix all hoisin sauce ingredients in a small bowl.
Remove the duck from the oven and let it rest for 6–8 minutes. Slice thinly with a sharp knife.
Serve the sliced Hoisin Duck with warm Chinese pancakes or rice, drizzle with the hoisin glaze, and top with spring onions and cucumber.