Begin by shredding the cooked chicken into bite-sized pieces.
In a large mixing bowl, combine Greek yogurt and mayonnaise.
Add the curry powder to the yogurt mixture and stir until well blended.
Incorporate the shredded chicken into the bowl.
Add diced celery, apples, raisins, and walnuts to the mixture.
Season with salt and pepper to taste.
Toss all ingredients gently to ensure even coating.
Let the salad chill in the refrigerator for at least 30 minutes.
Prepare a bed of green lettuce on serving plates.
Serve the chilled curry chicken salad on top of the lettuce.