Using a sharp paring knife, cut through the middle of each pork chop to the bone to make a pocket.
Combine cheese and mustard in a bowl. Divide cheese mixture and spoon into each pocket, pressing down to flatten chop. Sprinkle chops with pepper.
Warm oil in a large skillet over medium-high heat. Cook chops, turning once, until browned on each side, about 3 to 4 minutes per side. Remove from heat, cover pan and let stand until cheese has melted, 4 to 5 minutes.