Clean and julienne leeks. Dust leeks in flour/cornstarch and fry until golden brown, about 30 seconds. How to Cook Stir Fry Leeks (big onions) with beef - YouTube Make sure to cut through the fibers at a right angle; if they are cut on the diagonal, they'll flatten after cooking. See Cook's Note. Sift cornstarch and flour together. Cut the leek into 3 cm pieces. Begin stir-frying the leeks, starting … Simply use 1 teaspoon chicken soup stock granules and 1/3 teaspoon sesame oil instead. Drain on a paper towel, season with salt.