Rinse bok choy well and pat dry. Trim stem tips, quartered/halved/thirds depending upon size of the baby bok choy. (see video)
Slice garlic and minced ginger.
Place oil, ginger and garlic in a skillet or wok and turn heat to medium. As soon as the garlic begins to sizzle a bit (do not burn), add the Bok choy stems and a pinch of salt. Sauté for about three minutes.
Add bok choy greens and another pinch of salt. Stir to mix. Then add the red pepper flakes and mirin. Sauté for one more minute.
Turn off heat. Drizzle with a bit of toasted sesame oil. Serve immediately.