Wash the green beans and pat them completely dry with a clean towel; moisture prevents blistering. Trim off the tough stem ends. Finely mince the garlic and ginger (if using) and keep them in a small bowl near the stove. If using dried chilies, break them in half and discard some or all of the seeds if you prefer milder heat.
1 pound fresh green beans, 6–8 cloves garlic, 1–2 teaspoons fresh ginger, 1–2 small dried red chilies
In a small bowl, whisk together the light soy sauce, oyster sauce, Shaoxing wine, sugar, and water until the sugar dissolves. Set aside near the stove.
1 1/2 tablespoons light soy sauce, 1 tablespoon oyster sauce, 1 teaspoon Shaoxing wine, 1/2–1 teaspoon sugar, 2 tablespoons water
Place a large skillet or wok over medium-high to high heat and let it preheat for 1–2 minutes. Add the neutral oil and swirl to coat the bottom and sides. The oil should shimmer and move freely; a faint wisp of smoke is fine.
2–3 tablespoons neutral oil
Add the green beans in as close to a single layer as possible; they should sizzle on contact. Stir-fry for 6–8 minutes, tossing every 30 seconds or so, until the beans are bright green with browned or lightly blistered spots and are just tender-crisp. If they brown too quickly while still very hard, lower the heat slightly and cover for 1–2 minutes to help them steam through.
1 pound fresh green beans
Push the beans up the sides of the pan, leaving an empty space in the center. If the pan looks dry, add a small drizzle of neutral oil to the center to help the aromatics cook evenly.
2–3 tablespoons neutral oil
Add the minced garlic, minced ginger (if using), and dried chilies or red pepper flakes (if using) to the center of the pan. Stir constantly over medium-high heat for 30–45 seconds, just until very fragrant and lightly golden; do not let the garlic turn dark brown.
6–8 cloves garlic, 1–2 teaspoons fresh ginger, 1–2 small dried red chilies
Toss the green beans back into the garlic mixture until they are evenly coated with the aromatics. The beans should smell intensely garlicky and savory.
1 pound fresh green beans, 6–8 cloves garlic, 1–2 teaspoons fresh ginger, 1–2 small dried red chilies
Stir the prepared sauce, then pour it around the edges of the hot pan rather than directly onto the beans. Let it sizzle briefly, then stir-fry for 1–2 minutes, until the liquid reduces slightly and forms a glossy coating that clings to the beans without leaving a large pool of sauce in the pan.
1 1/2 tablespoons light soy sauce, 1 tablespoon oyster sauce, 1 teaspoon Shaoxing wine, 1/2–1 teaspoon sugar, 2 tablespoons water
Turn off the heat. Drizzle in the toasted sesame oil and the rice vinegar or black vinegar (if using), tossing well to coat. Taste a bean and adjust the seasoning: add a pinch more sugar if it tastes too salty or sharp, or a splash of soy sauce if you want more depth.
1/4 teaspoon toasted sesame oil, 1/2 teaspoon rice vinegar or Chinese black vinegar, 1 1/2 tablespoons light soy sauce, 1/2–1 teaspoon sugar
Transfer the green beans to a serving plate. Garnish with toasted sesame seeds and sliced scallions, if desired. Serve immediately while the beans are still hot and tender-crisp.
1 pound fresh green beans, toasted sesame seeds, thinly sliced scallions