Sprinkle the pork joint generously with the sea salt and leave it for an hour or so.
Rub half the butter over the pork and grate some nutmeg and pepper over it. (You could use ready-ground nutmeg at a pinch, but it doesn’t taste a tenth as good. Invest in a nutmeg grater.)
Heat a deep flameproof casserole and pop in the pork joint; brown it well on all sides. Spoon in the brandy and set a match to it to flame the meat.
Transfer the pork to a roasting tin, pour over the milk and roast in a preheated oven, 200°C/400°F (gas mark 6), for 30 minutes. Then add the walnuts and cook for about another hour, until the meat is tender.
Score the apples round their middles with a sharp knife and bake in the oven for the last 30 minutes or so on a separate dish with a knob of the remaining butter on each.
Lift out the pork. Thicken the pan juices with the cornflour, mixed with a little cold water, then strain the sauce into a jug. Carve the meat and serve it with the apples and some mashed potatoes. Hand round the sauce separately.