Preheat the oven to 350°F.
Rub the chicken pieces with oil and sprinkle all over with salt and pepper. Place on a baking rack on a lined baking sheet and roast for 50 minutes, or until internal temperature reaches 165°F. Set aside until cool enough to handle.
Remove the meat from the bones, discard the skin, and dice the chicken into large bite-size pieces, about ½"x½".
In a medium bowl, make the dressing by mixing together the mayonnaise, yogurt, curry powder, lime juice, honey, ginger, salt, and pepper.
In a separate, large bowl, add chicken, onion, mango, grapes, and cashews.
Add the dressing in increments, starting with about ½ a cup, gently stirring as you go. Depending on how much chicken you have, you'll most likely need about 1 to 1½ cups of the dressing. Add more or less as per your own desired consistency.
Cover with plastic wrap, or put in an air-tight container and place in the refrigerator for at least 1 hour, or overnight. The longer it sits, the more the flavors will meld. Let come to room temperature before serving.
Serve over a bed of lettuce greens, or as sandwiches using your favorite sandwich bread.