Wash the kale and dry it thoroughly. Strip the leaves from the stems and discard the stems. Stack the leaves and slice them into thin ribbons.
Toast the walnuts in a dry skillet over medium heat for 3–5 minutes, shaking the pan, until fragrant. Let them cool.
Whisk the olive oil, lemon juice, mustard, maple syrup, salt and pepper in a small bowl.
Put the kale in a large bowl with a pinch of salt and about a third of the dressing. Massage the leaves with clean hands for 2 minutes, until they darken and soften.
Core the apple and cut it into thin slices or matchsticks.
Add the apple, walnuts, cranberries and Parmesan to the kale, pour over the remaining dressing, and toss.