Heat half the vegetable oil in a wok or a frying pan over a medium-high heat, and stir-fry the onions, carrots and green beans for 5 mins. Add the peppers, broccoli and chicken, and stir-fry for 3 mins more.
Tip in the rice and stir-fry for another 4 mins until all the grains of rice have separated. Push the rice and vegetables to the side, then add the remaining vegetable oil to the other. Crack in the egg and scramble briefly before stirring into the veg and chicken mixture.
Stir in the sesame oil and oyster sauce to coat, then garnish with the spring onions and sesame seeds.