Method:
- Marinate the beef: In a small bowl, stir together the corn flour and soy sauce. Add the beef and gently stir to coat. Let stand at room temperature for ½ hour.

- Heat a wok or large skillet over high heat until a bead of water sizzles and evaporates on contact. Add the peanut oil and swirl to coat the bottom. Add the beef and stir-fry until fragrant. Set aside.

- Add the chopped red and green peppers, spring onion, onion and garlic and stir-fry for another minute. Add the beef and keep stirring to coat the chicken. Simmer until the sauce is slightly thickened, about 1 minute. Transfer to a plate and serve.