In a mixing bowl, pour the boiling water with the cornstarch and mix well with a wooden spoon. Add the taro and mash in well, but do not over mix to a smooth puree. Add the ham, scallions, lard and season. Check for seasoning. Season the chicken and place skin side down. Pat on a 1/2-inch layer of taro on the meat side. Coat both sides with cornstarch and fry until golden brown and the chicken is done, about 6 to 8 minutes. Season lightly and drain on paper towels. Cut each breast in half on the bias.
Tropical Sweet and Sour Sauce:
In a large saucepan coated lightly with oil on medium heat, saute the onions, carrot, garlic, ginger, and chiles. Stir and season. Cook until soft, about 5 minutes. Add the pineapple, mango and citrus juices/zest. Bring to a boil and simmer for a 20 percent reduction, about 15 minutes. Check for seasoning.