In a medium bowl, whisk together the oil, vinegar, shallot, mustard, garlic, salt (starting with the lesser amount), and pepper.
Add the kale, apple, and parsley (optional) and toss to coat with the dressing. Taste and adjust, adding more salt to taste, olive oil for richness, or parsley for herbiness and to balance the vinegar.
Best when fresh, but leftovers will keep in a sealed container in the refrigerator for 1-2 days. Not freezer friendly.