Marinate the chicken strips in the fridge for at least 10 minutes and up to 24 hours. For the stir-fry, cook the broccoli in 500ml/18fl oz boiling water until just tender (about 5 minutes).
Cook, stirring, until sauce is thickened and chicken and broccoli are well coated, 1 to 2 minutes more. Divide rice among plates or bowls. Spoon stir-fry over. Top with sesame seeds.
Cook and stir until the mixture boils and thickens. Stir in the chicken and cook until the mixture is hot and bubbling. Serve the chicken mixture over the rice.
Swirl in the remaining oil, add the garlic and ginger and stir-fry for no more than 10 seconds. Add the baby broccoli and the white and light green parts of the onions and stir-fry for 1 minute. Add ...