Bring stock and 3 cups water to a boil in a medium saucepan. Reduce heat to medium-low, and simmer 2 minutes. Season chicken with salt and pepper; add to stock mixture. Simmer, covered, until chicken is cooked through, about 14 minutes. Remove chicken using a slotted spoon; discard liquid. Let chicken stand until cool enough to handle. Cut into 1/2-inch pieces.Advertisement
Stir together mayonnaise, 1/4 teaspoon salt, 1/8 teaspoon pepper, the celery, apricots, almonds, if using, and apple in a medium bowl. Stir in chicken. Refrigerate chicken salad, covered, until cold, about 30 minutes. To serve in lettuce bowls, spoon about 1/2 cup chicken salad onto each leaf, using the smaller, inside leaves for kid-size portions. Any leftover chicken salad can be stored in an airtight container in the refrigerator up to 3 days.