Preheat the oven to 180°C.
Dry the pork thoroughly with kitchen towels and rub skin with salt.
Place the pork in a roasting tin with halved shallots and 250ml of cider.
Roast the pork for 45 minutes, adding water to the pan if the liquid dries out.
Increase oven temperature to 200°C and roast for another 45 minutes to crisp the crackling.
Combine 570ml cider and chicken stock in a pan and bring to a simmer.
Stir in honey and mustard, then season and reduce by three-quarters over one hour.
Stir in double cream to the sauce once slightly cooled.
Rest the cooked pork for 15 minutes and add pan juices to the sauce.
Remove crackling, carve meat into thick slabs, and serve with sauce, shallots, and sage.