Heat the oil in a skillet.
Once the oil is hot, stir fry the flank steak for 2 minutes.
Add the beef broth. Cover and bring to a boil.Simmer for 10 to 15 minutes.
Remove the cover and let the liquid completely evaporate.
Put-in the garlic and onion. Cook for 1 to 2 minutes.
Add the tomato. Cook for another 2 to 3 minutes.
Put-in the string beans, bok choy, and soy sauce. Stir and cook for 4 to 6 minutes.
Add sugar, salt and pepper to taste.
Transfer to a serving plate. Serve.
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