Tender beef slices are seared with generous amounts of garlic and finished with a savory soy glaze. Quick, high protein, and boldly flavored, this stir-fry is a family weeknight go-to.
Slice the beef sirloin thinly against the grain and pat dry to ensure good searing.
Mince the garlic cloves finely and slice the green onions; set aside for use at different cooking stages.
In a bowl, mix soy sauce, brown sugar, black pepper, and cornstarch until smooth to create the glaze.
Heat 1 tablespoon of oil in a large skillet or wok over high heat until shimmering, then quickly sear half the beef in a single layer, turning just until browned—about 1 minute per side; transfer to a plate and repeat with the remaining oil and beef.
Lower heat to medium; add garlic to the pan and stir-fry for 30 seconds, being careful not to burn it, then immediately return all beef to the pan.
Pour in the glaze and toss beef until evenly coated and the sauce has thickened, 1–2 minutes.
Stir in green onions, cook for 30 seconds longer, then serve immediately for best tenderness.