Put the diced chicken breasts, red onion, apple, ½ cup grapes, raisins and ¼ cup flaked toasted almonds in a large bowl.
In a small bowl, combine the mayonnaise, yogurt (crème fraîche or sour cream), curry powder, celery salt, salt, and freshly ground pepper. Whisk together until blended.
Stir the mayonnaise mixture into the chicken, vegetable, fruit and nut mixture until well mixed. It's easiest to toss the mixture lightly using two forks.
Serve on a bed of thinly sliced lettuces, garnished with extra halved grapes and flaked toasted almonds.