Peel the sweet potato and roll-cut diagonally into 1 1/2 inch slices.
Heat the oil in a wok or deep frypan to 375F or until a piece of scallion green or ginger sizzles noisily and browns quickly when tossed into the oil. Add the chicken and deep-fry for 2 min til golden brown. Remove the chicken to a sauce pan and add the rice wine and salt. Simmer over medium heat for 20 minutes. Add the soy sauce, sugar, sweet potato and stock and continue simmering, until the chicken is tender.
If too much liquid is left in the saucepan, reduce by boiling rapidly. Stir the dissolved cornstarch and add to the saucepan. Cook, stirring, until the sauce thickens. Sprinkle with the sesame oil, and serve.