Combine tamari, mirin, miso, fresh ginger, garlic and chilli in a bowl. Brush steak with a third of the sauce mixture.
Heat a wok over medium heat. Add half the oil. Swirl to coat. Cook steak, in two batches, in wok for 3-4 minutes each side for medium, or until cooked to your liking. Transfer to a plate. Stand for 5 minutes. Cut into thick slices.
Meanwhile, cook noodles in a large saucepan of boiling water following packet directions, until tender. Drain. Reserve 2 tablespoons cooking liquid.
Heat remaining oil in cleaned wok over high heat. Add bok choy, corn and onion. Stir-fry for 2 minutes or until vegetables are just tender. Add remaining sauce mixture, reserved cooking liquid and noodles. Stir-fry, tossing gently, for 1-2 minutes or until heated though. Serve noodle mixture topped with beef and sprinkled with pickled ginger.