1. If you’re using fresh Chinese egg noodles that are not precooked, cook them first, cut them in half, and set aside.

2. To prepare the choy sum, inspect it carefully, discarding or trimming any spoiled stems or leaves. Cut 1 inch (2.5 centimeters) off the base of each stalk and rinse the greens in several changes of the coldest possible water. If you’re using baby bok choy or baby Shanghai choy, inspect the heads carefully, discarding or trimming any spoiled stems or leaves. Cut 1/8 inch (3 millimeters) off the base of each head and rinse the greens in several changes of the coolest possible water. (Take care to clean baby bok shoy or Shanghai choy carefully, as it tends to have hidden pockets of sand where the leaves meet the center stem). Cut the cleaned choy sum into pieces 2 ½ to 3 inches (6 to 7.5 centimeters long): if you’re using baby bok choy or Shanghai choy, leave the heads whole or cut them in halves or quarters lengthwise, depending on size. Dry the greens in a salad spinner or set them aside to dry on a kitchen towel or on paper towels. They don’t need to be bone-dry; a little dampness is fine.

3. Heat the oil in a wok or 12-inch (30-centimeter) skillet (nonstick will work best) over medium heat. When it’s hot – it should appear slightly shimmery – ad the garlic and the sweet soybean paste (be mindful that the soybean paste may splatter a bit when it’s added to the hot oil) and sauté, stirring constantly with a large spatula, until the garlic is no longer raw but has not yet begun to change color, 1 to 2 minutes. If the garlic starts to turn golden, take the pan off the heat to cool for a few moments before continuing.

4. Add the shrimp to the skillet and stir-fry just until they begin to turn pink, about 2 minutes. Add the greens and raise the heat to high. Stir-fry vigorously until the greens just begin to wilt, 1 to 2 minutes. Add the bean sprouts (if using) and continue to stir-fry vigorously for another 15 seconds.

5. Reduce the heat slightly and quickly add the noodles, using your hands and detangling them as you drop them into the skillet. Stir the noodles well to combine them with the greens, bean sprouts, and shrimp. Add the warm water, soy sauce, and salt and stir well to combine. Cook, stirring constantly, until the noodles are hot and have soaked up all the liquid, about 2 minutes (Note that the noodles will have increased slightly in size once they have soaked up the liquid). Taste a noodle for salt, and add a pinch more if needed.

6. Transfer the noodles to a large platter or bowl and serve immediately. Although inauthentic, I like to top these noodles with freshly ground black pepper, which provides a nice layer of flavor.