Ingredients :

• Flank steak — It’s the ideal cut for this dish. Its long fibers cut into thin strips that cook quickly and stay tender if you don’t mistreat them. Always cut against the grain — otherwise you’re chewing on rope. If you can’t find flank, flat iron or thin sirloin will do the trick.
• Cornstarch — It does two things at once here: it creates a light crust on the meat during frying, and it thickens the sauce to give it that characteristic shine. Don’t replace it with flour — the result would be pasty and dull.
• Sweet chili sauce — This is the heart of the Beijing sauce. It brings both sweetness and a subtle spicy background, without being aggressive. The Mae Ploy brand is a reliable classic. Avoid overly industrial versions that are just sugar and coloring.
• Hoisin sauce — Think of it as an Asian barbecue sauce — thick, dark, with a sweet-savory depth that gives body to the whole dish. A little goes a long way. Lee Kum Kee is a solid brand and easy to find.