Place the kale in a mixing bowl. Add olive oil and a small pinch of salt. Massage with your hands for about 1 minute until softened and slightly darkened.
In a small bowl, stir together Greek yogurt, Dijon mustard, lemon juice, and black pepper until smooth. Adjust seasoning if needed.
Lay one tortilla flat on a clean surface. Spread a thin layer of the yogurt dressing across the center, leaving space around the edges.
Add a layer of massaged kale, followed by sliced chicken and a few thin apple slices. Sprinkle with optional walnuts, red onion, or shredded carrots if using.
Fold the sides of the tortilla inward, then roll tightly from the bottom up to form a wrap.
Slice in half if desired and serve immediately, or wrap tightly in parchment paper or foil for storage.
