Preheat the slow cooker if necessary; see the manufacturer's instructions. Trim the thinnest end off each pork tenderloin so each is 23 cm (9 inches) long, reserving the trimmings. Make a slit along the length of each and open out flat.
Put the pork trimmings into a food processor with the bread, onion, garlic, ginger, spice and salt and pepper and mix until finely chopped. Spoon half the mixture along the length of one piece of pork, press the prunes on top, then cover with the rest of the stuffing and the remaining tenderloin. Season, then wrap the bacon around the pork and tie in place with string.
Heat the oil in a large frying pan, add the pork and shallots and fry, turning the pork until golden all over. Transfer to the slow cooker pot. Make a smooth paste with the cornflour and a little cold water, then add to the pan with the remaining ingredients. Bring to the boil, stirring until thickened, then pour over the pork.
Cover with the lid and cook on high for 3½–4 hours or until the pork is cooked through and tender. Transfer the pork to a serving plate. Serve cut into thick slices, with the shallots and sauce, accompanied with steamed asparagus and creamy potato dauphinoise.