Tie up the lean pork loin (about 1kg or so) and stick some sliced garlic (2 cloves) and sage leaves under the string. Season with salt and pepper.
Melt some butter in a large, very hot frying pan, then add the whole joint of pork. Brown on all sides before carefully pouring in half a glass of white wine.
When the initial frazzle is over, put the pork and the buttery juices into a lined ovenproof dish. Cover with a lid or tinfoil, then roast at 190 degrees for about an hour.
Meanwhile, slice and peel about four quinces and an onion. Mix with some chopped parsley. After the pork has had its first stint in the oven, surround it with the quince-onion-parsley mix. Pour over half a pint of water. Cover again, then cook for a further 45 mins to an hour, but check the meat from time to time with a knife to see whether it is becoming tender. Turn the oven down if it is browning too much.
When the meat is ready, remove it from the roasting tin; cover and keep it warm while you make the sauce. It’s not hard – just stir a tablespoon or two of creme fraiche into the quince mix, sprinkle the quince with a couple of teaspoons of sugar and let it cook through in the oven for 15 minutes while the pork rests.
Slice the pork and sprinkle with more parsley. Serve with the roasted quince and sauce.