Mix the butter with the cheese, form into a log and refrigerate. Season the pork chops with salt, pepper and brush both sides with some of the olive oil. In a large bowl, mix together the onions, pears, potatoes, some thyme sprigs and the rest of the olive oil with salt and pepper. Put this mixture in a baking dish and top with the pork chops. Bake in a 425 degree oven for 15 minutes. Remove from the oven and sprinkle the pear slices with brown sugar. Turn the pork chops over. Return the dish to the oven and continue to bake for 30-40 minutes. Serve the chops with a slice of roquefort butter on top.