In a large bowl, toss together the chicken, celery, apple, cashews, and currants.
In a small bowl, whisk together the yogurt, mustard, lemon juice, curry powder, salt, pepper, and ginger until smooth.
Pour the dressing over the chicken mixture and toss until evenly coated. Taste and adjust the seasoning if needed.
Spoon the salad into butter lettuce leaves and sprinkle with hemp hearts, if desired, for a nutrient-rich crunch.