Lay out your slices of bread. Add 1 slice of cheese to 2 slices of bread. Add apple slices on top of each slice of cheese (divide the apple slices in half between 2 sandwiches). Top with another slice of cheese, and then place the remaining bread slices on top. Slather butter on the top piece of bread. Heat your skillet over medium heat, and lay the sandwiches with the buttered bread touching the skillet. Butter the top piece of bread now. Place a sandwich press or heavy bottom skillet on top of the sandwiches to press them down. Cook for 3-4 minutes on first side, or until browned. Flip carefully and cook 2-3 minutes on the other side, allowing to brown (careful – second side usually cooks faster). Slice sandwiches in half and serve immediately!