Separate whites and greens of the spring onions (scallions), and cut into 2-inch sticks.
Heat 1 and ½ teaspoons oil in a wok or frying pan over high heat.
Add onions and whites of spring onions (scallions). Stir fry for about 30 seconds. Remove from pan.
Add remaining oil. Once hot, add beef, and stir fry for about 3 minutes or until the beef slices are browned and cooked through.
Add garlic and stir fry for 30 seconds.
Pour in stir fry sauce and cook for about 1 minute.
Add cornstarch (corn flour) slurry, and stir fry for another 2 minutes or until the sauce thickens.
Add cooked onion and spring onions (scallions). Add ground black pepper. Heat through.