1. Pre heat oven 180oC, Fan 160oC, Gas mark 4
2. Firstly prepare the duck by placing it breast side down on a chopping board . Using a strong pair of scissors, cut down either side of the back bone from neck to tail. Remove the back bone and save for stock. Gently prise apart and push down on the breast bone to flatten. Turn the duck over so breasts are facing upwards.
3. Prick the skin around the legs and then season the duck both sides with salt, pepper and half of the paprika .
4. Place on a baking tray, breast side up and place in the oven. Cook for 1 hr 30 minutes
5. Whilst the duck is cooking prepare the piri piri marinade. Place the garlic, remaining paprika, chilli, vinegar, oil, sugar and lemon into a blender and blitz. Use this marinade to baste the duck with 5 or 6 times while it is cooking.
6. Approx 30 mins before the duck is due to be ready, take a deep sided baking tray big enough to hold the potatoes and pour in the duck fat. Place the tray into the oven and after 10 mins, once the oil is hot, take out and carefully put your potatoes into the tray. Gently sprinkle the cumin seeds plus some salt and pepper over the potatoes and return to the oven. They will be ready in 20 -30 minutes
7. When the duck is cooked, remove from the oven and leave in a warm place to rest for a few minutes, pour over any remaining marinade.
8. When you are ready, serve the duck with the potatoes along with some vegetables or a mixed salad.
9. For a chargrilled finish place the duck on hot large griddle plan at the end or in the summer, place on the barbecue.