01 - Whisk together soy sauce, mirin, sesame oil, and sugar in a small bowl until sugar dissolves completely. Set aside for later use.
02 - Heat neutral oil in a large skillet or wok over medium-high heat until shimmering.
03 - Add sliced onions to the hot pan. Stir fry for 2 minutes until they begin to soften and turn translucent.
04 - Add minced garlic and ginger to the pan. Cook for 30 seconds, stirring constantly, until fragrant but not browned.
05 - Add zucchini pieces to the pan. Stir fry for 3 to 4 minutes until just tender but still crisp-tender.
06 - Pour the prepared sauce over vegetables. Toss to coat evenly and continue stir frying for 1 to 2 minutes until sauce slightly thickens and vegetables appear glossy.
07 - Remove from heat immediately. Sprinkle with green onions and toasted sesame seeds. Serve warm as a side dish or over steamed rice for a light main course.