Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper or a silicone mat and lightly oil it.

In a mixing bowl, combine ground chicken, panko, egg, green onions, garlic, ginger, soy sauce, sesame oil, rice vinegar, and red pepper flakes if using. Season with a pinch of salt and pepper and mix gently until just combined.

With damp or lightly oiled hands, shape the mixture into 18–20 meatballs (about 1 to 1½ inches). Arrange evenly on the prepared baking sheet.

Bake for 15–18 minutes, or until lightly browned and the internal temperature reaches 165°F (74°C).

While the meatballs bake, make the glaze: In a small saucepan whisk soy sauce, honey (or brown sugar), rice vinegar, sesame oil, grated ginger, and minced garlic. Bring to a gentle simmer over medium heat.

Stir cornstarch and water together to form a slurry. Whisk the slurry into the saucepan and cook 30–60 seconds until the glaze is glossy and thick enough to coat a spoon. If too thick, whisk in a tablespoon of water.

Transfer hot meatballs to a large bowl, pour the warm glaze over them, and toss gently with tongs until evenly coated.

Garnish with sesame seeds and chopped green onions. Serve hot as an appetizer or over rice or noodles for a main meal.

Air fryer option: Cook shaped meatballs at 375°F (190°C) for 12–14 minutes, shaking the basket halfway; toss in warm glaze and serve.