Butter one side of each bread slice. Spread the unbuttered side of 2 of the bread slices with mayonnaise and mustard; divide and top with ham, apples and cheese. Top with the other 2 slices of bread, buttered side up.
Set a large, non-stick skillet over medium low to medium heat. Add the sandwiches and cook 3 to 4 minutes per side, or until the cheese is melted and the bread is nicely toasted. Slice the sandwiches in half or quarters and serve.