Mix the soy sauce and sugar together in a small
bowl, stirring until the sugar has dissolved.
Trim
any fat away from the chicken and cut into thin
strips. Place the meat in a shallow dish and spoon
the soy mixture over it, turning to coat. Marinate
in the refrigerator for 20 minutes.
Heat the oil
in a wok and stir-fly the chicken for 2 to 3
minutes, until golden
brown. Add the onions and garlic and cook for a
further 2 minutes. Add the bean sprouts, cook for 4
to 5 minutes, and then add the sesame oil.
Mix the corn flour and water to form a smooth paste. Pour the
stock into the wok, add the corn flour paste and
bring to the boil, stirring until the sauce is
thickened and clear. Serve hot.