Whisk together the cornflour and water in a small bowl. Mix in the soya sauce and 2 tablespoons oil, and set aside.
Heat the remaining oil in a wok over medium high heat. Stir-fry the carrot, capsicum and broccoli for about 5 minutes. Stir in the corn, garlic, spring onions, beansprouts and the soya sauce mixture. Cook and stir for about 5 minutes or until vegetables are tender but crisp. Serve immediately.