Stir curry powder in a small skillet over medium heat until fragrant, about 30 seconds. Transfer to a medium bowl. Add mayonnaise, yogurt, chutney, ginger and orange peel. Whisk to blend. Stir in chicken, grapes, green onions, and walnuts. Season salad to taste with salt and pepper.
Place one lettuce leaf on each of 4 plates. Top each lettuce leaf with salad. Garnish each plate with grape clusters.