Thinly slice the chicken. In a small bowl, combine cornstarch with stock and soy sauce. Heat oil in wok, stir fry garlic and ginger until golden. Add chicken and stir fry 3-4 minutes, transfer to a bowl. Reheat oil;add bok choy and baby corn. Stir fry about 4 minutes, until bok choy is slightly softened and corn is lightly browned. Return chicken to wok with cornstarch mixture and pepper; cook, stirring to thicken slightly. Serve with steamed rice.