Preheat the oven to 200 degrees C. Peel and dice the parsnips.
Once the pork joint is cleaned, rub salt into the skin to help create a crisp crackling. Put the thyme on the base of a baking dish then place the pork on top and roast for 45 minutes.
Parboil the parsnips for 5 minutes, adding them to the roasting tin after the pork has cooked for 45 minutes. Baste them in some of the cooking juices from the pork. Cook the pork and parsnips for a further 45 minutes. Remove pork and parsnips from oven and leave standing for 10 minutes.
Place the cider in a saucepan. Remove thyme from roasting tray and drain the excess fat from the tray into the saucepan. Bring to a boil for 2-3 minutes then stir in the cream. Continue to heat for about 5 minutes, stirring, strain the sauce into a jug. Slice the pork loin and serve with the parsnips and cider cream sauce.