If using smaller bok choy, cut them into halves lengthwise. Any pieces that look a bit too big can be cut into quarters. This will make them easier to eat and help loosen sand and dirt during washing.
If using medium or large bok choy, separate the bulbs into individual stems. Trim away the tough base. If they’re very large, cut the bok choy at a slight angle into 1-inch pieces. Note that it’s easier to wash large bok choy leaves/stems before cutting.
Throw the bok choy into a large bowl with lots of cold water. Agitate the veggies with your hands and/or use your faucet sprayer to loosen any dirt. Soak for 5 to 10 minutes (you can leave them for longer if you are prepping other things).
Scoop the veggies out of the water into a colander, and rinse the bowl clean of any sand. Repeat the process until you don’t see any dirt on the leaves or at the bottom of your bowl—usually 2 more times will do the trick. On the second or third soak, you can run your fingers on the stems to loosen any stubborn sand.
After the final wash, give your colander of bok choy a few good shakes to release any excess water.
Heat your wok or a large pan over low heat, and add the oil and ginger. If you prefer a stronger garlicky flavor, add the garlic now. You can let it sizzle in the oil for 10-15 seconds, but don’t let it brown, or it will turn bitter. Add the veggies when the garlic is still white. If you like a fresher, more mild garlic flavor, add it in after salting the vegetables.
Add the veggies, and increase the heat to high. Stir-fry using a scooping motion so the oil and aromatics are evenly distributed.
Next, add salt, sesame oil (if using), and the white pepper. Stir-fry for another 1-2 minutes. Finish off with the cornstarch slurry, adding it to the center of the vegetables. Toss the vegetables until they are glistening. Plate and serve immediately.