Wash bok choy: Cut baby bok choy in half (or quarters if very big) and place into a large bowl with water. Swirl the bok choy around to rinse out the dirt from between the leaves. Drain and repeat a few times until you don't see dirt in the water. Drain bok choy and shake off excess water, but you don't need to pat dry.
Mix sauce: Whisk sauce ingredients together in a bowl and set aside.
Stir fry: Heat oil in a wok or pan over medium high heat. Add ginger and stir for about a minute until fragrant.
Add bok choy (be careful of splashing, keep your face away from the wok) and stir to coat with the oil, then cover to wilt. Stir every minute or so until tender (about 5 minutes total).
Give the sauce a quick whisk then pour into the wok. Toss to combine and cook until thickened.
Turn off the heat and drizzle sesame oil over. Taste and add more salt or pepper as desired. Sprinkle with sesame seeds if desired.