Butter each side of the bread slices. In a large skillet, cook the bread over medium-low heat, turning once, until just golden, about 5 minutes; season one side of each slice with pepper. Sprinkle the cheese over 1 bread slice, then set the other slice into place. Cook the sandwich, turning once, until the cheese is melted, about 3 minutes. Serve immediately with the mustard and pickles.