Trim the very bottom of each bok choy head and halve lengthwise. Swish in a large bowl of cold water, changing the water twice, to remove grit trapped between the layers.

Dry the greens well. Spin in a salad spinner, then pat with clean towels. Excess wash water drops the pan temperature and steams the bok choy instead of searing it — this is the single biggest quality lever in the dish.

Heat a wok or large heavy skillet over high heat until a drop of water evaporates on contact. Add the neutral oil and swirl to coat.

Add the bok choy cut-side down in a single layer. If it does not fit, work in two batches — crowding steams. Sear undisturbed about 2 minutes until the cut sides pick up light char.

Stir-fry 2 minutes more, tossing, until the leaves wilt and the stems are tender-crisp. Push the greens to the sides, add the garlic to the oil in the center, and stir 20 seconds until fragrant but not browned.

Sprinkle over the salt, sugar, and white pepper (if using); toss to coat. Drizzle with sesame oil off the heat. Serve immediately.