Mix the soy sauce, sesame oil and cornflour in a small bowl with 2 tablespoons of cold water to make a sauce. Set aside.
Cook the noodles or rice according to the packet instructions.
Heat the vegetable oil in a wok or large frying pan over a high heat until smoking. Add the sliced chicken and stir-fry for 3-4 minutes until golden and cooked through. Remove and set aside.
Add the red pepper, carrot and mangetout to the wok. Stir-fry for 2-3 minutes until just tender with a bit of bite.
Add the garlic and ginger, stir-fry for 30 seconds until fragrant.
Return the chicken to the wok. Pour in the sauce and toss everything together for 1 minute until the sauce thickens and coats everything in a glossy glaze.
Serve immediately over noodles or rice, topped with sliced spring onions.