Onion is the main vegetable here: one large yellow onion, sliced thin, stir-fried until soft at the edges but still holding its shape. A small carrot cut into matchsticks adds colour.
The beef is seared on its own first and rested while the onion cooks, then everything meets in a quick soy and oyster sauce thickened with a teaspoon of cornstarch.
The Wok Sequence
Everything is ready before the heat goes on; after that the whole dish takes about ten minutes.
Before the heat
Soy, oyster sauce, water, brown sugar, cornstarch and sesame oil whisked
Ready to pour in one go.
High heat
1 lb thin-sliced flank steak in 1 tbsp oil
Browned and at least 145°F, then out to rest.
Same wok
1 large sliced onion and 1 carrot in matchsticks
Until the onion softens at the edges but keeps its shape.
1 to 2 minutes
The beef and the sauce
Tossed until glossy and lightly thickened.
Off the heat
Green onion pieces and sesame seeds
Served immediately.
Ingredient Notes
- Flank steak
- One pound, sliced thin against the grain so it cooks through in moments.
- Yellow onion
- One large onion, thinly sliced; it is the dominant vegetable of the dish.
- Soy and oyster sauce
- Three tablespoons low-sodium soy with a tablespoon of oyster sauce. Both may contain wheat, soy or shellfish.
How to Make It
Sauce whisked
Whisk the soy sauce, oyster sauce, water, brown sugar, cornstarch and sesame oil together.
Flank steak seared to 145°F and rested
Heat 1 tbsp neutral oil in a wok or skillet over high heat. Stir-fry the flank steak until browned and at least 145°F, then lift it out and let it rest briefly.
Onion and carrot stir-fried
Add the rest of the oil with the onion and carrot and stir-fry until the onion is soft at the edges but still holds its shape.
Beef back in with the sauce
Return the beef, pour in the sauce and toss for 1 to 2 minutes until glossy and lightly thickened.
Green onion and sesame to finish
Fold in the green onions and sesame seeds and serve straight away.
Why This Recipe Works
- Slicing flank steak thinly against the grain keeps each strip tender after a fast, hot sear.
- Cooking the beef separately lets it brown rather than stew with the onion's moisture.
- Whisking the sauce ahead means it can go straight in and thicken within a minute or two.
- Brown sugar in the sauce helps the onion caramelise lightly at the edges.
Frequently Asked Questions
How cooked should the beef be?
At least 145°F. Thin strips get there fast over high heat; rest them briefly while the onion cooks.
Does the sauce contain allergens?
Soy sauce and oyster sauce may contain wheat, soy and shellfish, so check the labels.
Can I add other vegetables?
This recipe keeps to onion with a little carrot so the onion stays the main vegetable.
Success Tips
- Firm the steak in the freezer for 15 minutes to make thin slicing easier.
- Get the wok smoking hot before the beef goes in, and sear in batches if needed.
- Pull the onion while it still has a little bite; it softens more in the sauce.
Serving Ideas
Serve piled on a plate straight from the wok, with the glossy onion strands through the beef and green onion and sesame on top.
