- Blend 1¾ tsp oil, cornstarch, sugar and salt.
- Add beef and toss to coat thoroughly.
- Let stand for 20 minutes.
- Heat wok until hot.
- Add remaining oil and heat until oil begins to smoke.
- Add beef and stir fry until beef is just cooked through, about 2 minutes.
- Remove beef with slotted spoon and discard all but 1 tbsp oil.
- Reheat wok and add scallions and beef.
- Stir fry quickly, 30 seconds.
- Add chicken stock and stir fry 30 seconds more.
- Add mango and toss mixture until the mango is warm.
- Serve immediately over rice.