Preheat the oven to 230C/210C Fan/Gas 8.
Bring the potatoes to the boil in a large pan of salted water, then simmer for 6-8 minutes. Drain well and set aside until cool enough to handle, then peel away the skins and chop the flesh into 0.5cm/¼in slices.
Cut one apple in half and then into thin slices.
Cover the bottom of an ovenproof frying pan with pancetta lardons. Add a layer of sliced potatoes on top, then a layer of sliced apple, and continue with alternate layers of pancetta, potatoes and apple, seasoning as you go with salt and freshly ground black pepper.
Sprinkle over the thyme, then slice off the top rind of the Reblochon cheese and place the whole cheese, cut side down, into the centre of the pan. Scatter the butter around the cheese.
Cook the tartiflette in the oven for 20-25 minutes, or until the cheese has melted and the pancetta is crisp.
Meanwhile, heat a large griddle pan over a high heat. Season the pork chops with salt and freshly ground black pepper. When the pan is hot, add the pork chops and cook for 6-8 minutes on each side, giving each chop a quarter-turn during cooking on both sides, until the chops are cooked through and browned on both sides.
Cut the remaining 2 apples in half and place them, cut sides down, into the pan alongside the pork chops, for the last 2 minutes of cooking, until chargrill marks appear.
Serve the pork chops with half an apple and the tartiflette.