1. Preheat the oven to 220°C/ 200°C fan/ Gas Mark 7.
2. Boil the potatoes (starting in cold water) for 5-6 minutes or until semi-tender.
3. While they boil melt the butter in a small pan and add the grated Bramley apple with a splash of water, the lemon peel and sugar. Cook until soft and beginning to catch and colour on the bottom of the pan. The catching and slight browning of the apples is important to the taste. Stir vigorously until pureed and season with a little salt and pepper. Put to one side.
4. Pour the sunflower oil into a roasting tray and get it very hot but not smoking.
5. Drain the potatoes and toss them with 2 tbsp plain flour in a sieve so that their edges crumble. Put them in the roasting tray with the hot oil, season generously with salt, baste them, then roast in the oven. After 15 minutes throw in the rosemary stalks and garlic and quickly turn them through the potatoes and continue to roast them for another 15 minutes or until deep golden.
6. While the potatoes cook, season the duck skin with plenty of salt and oregano. In a small, pan pour in a little sunflower oil. The duck skin should sizzle immediately but not burn. Over a low-medium heat cook on the skin side only for 14 minutes until the skin is deep golden orange and crisp. Pour off any excess fat from time to time. Turn over and cook for 4 minutes on the flesh side. Allow to rest skin side up, for 5 minutes. Fry the sage leaves, on both sides, briefly in the duck fat until crisp.
7. Slice the duck. Spoon some hot apple sauce onto a warm plate and lay the duck on top crispy side up. Place the sage leaves on the top.
8. Add some potatoes and garlic to the plate along with a good handful of watercress dressed in a little red wine vinegar and salt.
Our thanks to Bramley Apples for providing this recipe.