Mix peeled pears with sugar and let sit for 12 hours at room temperature.
Drain pear juice into a pan, boil for 5 minutes, pour back over pears, and sit for 12 hours.
Repeat the draining, boiling, and soaking process for 12 more hours.
Repeat twice more, then boil syrup until reduced by two-thirds and caramelize pears in it for 20 minutes.
Stir 10 drops of mustard oil into cooled pears and mature in jars for 2-3 weeks.
Preheat the oven to 180°C.
Roast duck bones in a tray until they are well browned.
Sauté shallot and garlic in olive oil, add herbs, peppercorns, and Madeira, then reduce to a glaze.
Add roasted bones and stocks to the pan, simmer until reduced to 100ml, strain, and chill.
Toast whole spices for the spice bag and wrap them in muslin cloth.
Marinate cabbage with sugar, Port, wine, and spice bag under a weight for 24 hours.
Cook onion and apples in duck fat, add cabbage and marinade, then reduce to a glaze with jelly.
Increase oven temperature to 200°C.
Stack sliced potatoes into four neat rectangles measuring 15cm by 7cm and season well.
Brown potatoes in oil, add hot duck sauce, and roast for 5 minutes until tender.
Render duck breast skin-side down in a pan, add butter, cook to medium-rare, and rest before roasting for 5 minutes.
Serve sliced duck on a bed of cabbage and potatoes, garnished with mustard fruits.