Cut the chicken into thin strips across the grain; set aside. Blanch the carrots in boiling water for 2 minutes. Lift out with a slotted spoon, immediately refresh under cold running water, then drain. Repeat with the baby corn.
Heat 2 tbsp of the oil in a wok or large, deep frying pan over a moderate heat. Add the chicken strips, increase the heat to high and stir-fry for 3-4 minutes or until lightly coloured on all sides. Remove the chicken with a slotted spoon and transfer to a plate.
Heat the remaining oil in the wok on a moderate heat. Add the red pepper and garlic and stir-fry for 2-3 minutes until softened, but not coloured.
Add the carrots, corn and mangetout. Increase heat to high and stir-fry for 3-4 minutes, until tinged brown. Add the chicken and it juices and toss over the heat for 1 minute. Serve with rice.