Look for the long muscle fibers running through the flank steak and cut across them, not with them. Thin slices against the grain are the difference between tender and chewy. Half-freezing the steak for 20 minutes makes it easy to slice thin.
A stir-fry lives or dies on heat. Get the wok as hot as your stove allows and don't crowd it β work in batches if you must, so the beef sears instead of steams.
A spoonful of chili crisp is our favorite way to add heat right at the table β it spiced up the beef-and-snap-pea duo perfectly. Pass the jar and let everyone dial in their own.