Place the chicken in a saucepan with the onion, garlic, salt and peppercorns and add water to cover.Bring to a boil over high heat, reduce heat to low, cover and simmer until the chicken is just cooked through, about 25 minutes.Allow chicken to cool in the poaching liquid.Remove the skin and bones and shred the meat into large, bite-size pieces. Set aside in a large bowl.Add the celery, scallions, apple or grapes, raisins and cashews to the chicken.In a medium bowl, combine yogurt, mayonnaise, preserves, curry powder, vinegar, salt, ginger, and cayenne pepper.Pour on top of the chicken and salad ingredients and combine to coat well with dressing. Adjust seasonings to taste.Store leftovers in the refrigerator for up to 3 days.