Preheat the oven to 400 degrees. Wash the sweet potatoes, scrubbing them well to remove any dirt or soil. With a fork, prick the sweet potatoes. Place on the oven rack; bake about 45 minutes, or until a knife inserted in the center goes in easily. Remove the potatoes from the oven.
Carefully cut off 1/3 of each potato lengthwise. Scoop out and remove the pulp from the potato, leaving a 1/4-inch-thick shell. Scoop out all pulp from the potato tops, and discard the tops.
In a large bowl, mix well the potato pulp, butter, salt, smoked chicken and cayenne. Fill the potato shells with the hot mixture, mounding it slightly. Serve immediately.
Adapted from The Perfect Potato, by Diane Simone Vezza