We’ve done countless kitchen experiments with flank steak over the years in pursuit of tender, flavorful stir-fries. And we’ve learned that there are three essential keys to success.
1. Cut the steak correctly. First, cut your steak into thirds with the grain. Then slice each third very thin against the grain. This keeps the meat from becoming overly chewy and creates little pockets for marinade and sauce to cling to.
2. Add a bit of cornstarch to your marinade. This technique, called “velveting,” creates a superthin coating around the meat to help keep it juicy and tender.
3. Don’t overcook the steak. In this recipe, we call for cooking the steak in batches for about 2½ minutes per batch. Be sure to remove it from the heat immediately: Overcooked beef is chewy and tough, which is not what you want.