Pierce potatoes with a fork; arrange in a circle on paper towels in microwave oven. Microwave at HIGH 10 minutes or until done, rearranging potatoes after 5 minutes.
While potatoes cook, combine sour cream and 2 tablespoons onions; set aside.
Place chicken in a microwave-safe bowl; cover with plastic wrap (do not allow plastic wrap to touch food).
Remove potatoes from microwave; place chicken in microwave. Microwave at HIGH 2 minutes or until thoroughly heated.
Slice potatoes lengthwise, cutting to, but not through, other side; fluff with fork. Top each potato evenly with chicken, sour cream mixture, cheese, and remaining onions.
