Wrap the slices of pancetta around the pork fillet and then truss it, leaving a gap of couple of centimetres between one loop of string and the next. Insert the sprigs of thyme here and there under the string. Lay the meat on a chopping board and, using a sharp knife, slice it between the loops of string, creating “medallions” that are tied around the middle. In a large, heavy-bottomed frying pan, sauté the clove of garlic “in camicia” (literally “with its shirt on”, simply crushed with the palm of your hand, without removing the skin) with 2 spoonfuls of olive oil. As soon as the garlic begins to brown, remove it and put the medallions into the pan. Season with salt and pepper, cook for 5 minutes and as soon as they become golden brown turn them over. Season with salt and pepper again, add the apple, cut into fairly thin slices, and the finely sliced onion. When the meat has browned on the other side as well, turn up the heat, pour in the Vin Santo and let it evaporate. Now remove the medallions and set them aside; leave the apple and onion to cook, in the end they should be caramelised. Put the medallions back into the frying pan, toss them briefly with their “sauce” and serve nice and hot.