Place a wok or wide frying pan over high heat until hot. Add oil swirling to coat sides. Add ginger root and garlic. Cook, stirring, until fragrant, about 15 seconds. Add chicken, peas, carrots, and onions; stir 1 minute. Add rice; stir to separate grains with back of spoon. Mix well. Stir in soy sauce, sesame oil, and pepper; cook until thoroughly heated.