Marinade the beef for at least 10 mins.

Mix the sauce ingredients, set aside.

In a wok, heat up the oil and cook the beef until brown (should still be pink inside). Set aside.

Add onion and pepper to the remaining oil in the wok, cook for a min or so.

Put the beef back into the wok, stir fry for another 2 mins until beef is fully cooked.

Pour the sauce and stir until it's thick.

Sprinkle more black pepper for the flavour. Serve with rice.