Arrange salad leaves on a large platter; sprinkle top with onion, nuts and blue cheese.
In a small bowl, combine apple slices, balsamic dressing and parsley. Add apples to salad.
Drizzle blue cheese dressing over top of salad and top with crumbled prosciutto. Serve.
Tips: For a lighter alternative, try Marzetti Simply Dressed & Light Blue Cheese.