Slice steak into bite-size pieces.
Combine the marinade ingredients in a shallow bowl. Add steak and stir to coat with marinade for 1 hour at room temperature (or overnight in refrigerator)
Heat wok over med-high heat. Add oil. Stir-fry the shallot, ginger and chile for 1 minute.
Increase heat to high and add the beef and marinade. Stir-fry for 3-4 minutes. Add the bok choy stalks and stir-fry for 1 minute. Add the leaves and stir-fry for 1 minute.
Make a paste with cornstarch and water. Add to wok. Stir-fry for 1 minute. The liquid will thicken slightly.
Serve immediately. Enjoy with a sprinkle of cilantro!