Shred the cook cooked chicken. Make sure the chicken has cooled completely before mixing.
Chop the apple, almonds (if using) and quarter the grapes.
Toss the fruit and nuts with the chicken in a large mixing bowl. Stir them all together until evenly distributed.
In a small bowl, make the dressing by stirring together the mayonnaise, sour cream, sugar, garlic powder, curry, pepper and lemon juice. Stir for a couple of minutes to be sure that all of the dressing ingredients are smooth and that the sugar has dissolved. Salt and pepper to taste.
Pour the dressing over the chicken and fruit mixture. Use a large spoon to toss it all until the chicken is thoroughly covered and completely coated. Taste it to make sure it is well seasoned. If not, season with salt.
Refrigerate for at least 2 hours or until the salad is thoroughly chilled. The flavors will be even better if you let the chicken salad refrigerate overnight.
Garnish of chopped green onions. Serve with bread or on a bed of fresh salad greens.