In a large skillet over medium heat, warm the vegetable oil. Add the onions and season them with half of the salt and pepper. Toss to mix well and cook until they are soft and well browned, about 15 minutes. With a slotted spoon, transfer the onions to a bowl and set them aside.
Preheat the broiler on high. Season the chops with the remaining salt and pepper. Add a little more oil to the pan if needed, then raise the temperature to medium-high. Add the chops and cook for 3 to 4 minutes per side, until they are golden brown.
Under the broiler, toast the buns on the cut sides only, until lightly browned. On each bun, place a pork chop and then top it with one-sixth of the onions. Serve immediately.