Mix together the soy sauce, sesame oil, rice vinegar and honey in a glass or ceramic bowl, add the tofu and toss to coat. Cover and leave to marinate in the refrigerator for 1 hour. Drain the tofu, reserving the marinade.
Meanwhile, bring a large saucepan of water to the boil, add the broccoli florets and carrots and blanch for 2 minutes. Drain and then plunge the vegetables into a bowl of iced water. Drain again and set aside.
Spray a nonstick wok or large frying pan with cooking spray and heat over a medium-high heat. Add the marinated tofu and stir-fry for 5 minutes until lightly browned. Add the onion, spring onions, ginger and garlic and stir-fry for 30 seconds. Stir the blanched broccoli and carrot into the pan along with the mangetout, baby corn and water chestnuts and stir-fry for 1–2 minutes.
Mix together the cornflour, stock and reserved marinade in a small bowl until smooth and add to the pan. Bring to the boil and cook, stirring constantly, for about 2–3 minutes until slightly thickened. Serve with rice or noodles.