In a large mixing bowl, combine the ground beef, breadcrumbs, chopped green onions, egg, minced garlic, grated ginger, and a pinch of salt and pepper. Using your hands or a spatula, mix thoroughly until the ingredients are well integrated.
Preheat your oven to 400°F (200°C) to ensure it's hot enough for baking the meatballs.
Take a small amount of the meat mixture and shape it into 1-inch meatballs, ensuring they are compact. Arrange them on a baking sheet lined with parchment paper to prevent sticking.
Bake the meatballs in the preheated oven for about 15-20 minutes, or until they are fully cooked and have a golden brown exterior.
While the meatballs are baking, create the teriyaki glaze. In a small saucepan set over medium heat, combine the teriyaki sauce, sesame oil, and rice vinegar. Stir the mixture occasionally and allow it to simmer for approximately 5 minutes until it thickens slightly.
Once the meatballs are cooked, remove them from the oven and transfer them to a large mixing bowl. Gently pour the teriyaki glaze over the meatballs, tossing them lightly until they are evenly coated in the sauce.
To add an extra sticky texture to your meatballs, place them back on the baking sheet and broil for an additional 1-2 minutes. Keep a close watch to prevent burning and achieve the desired glaze.
After broiling, remove the meatballs from the oven and sprinkle them generously with toasted sesame seeds. If you like, add fresh cilantro for a pop of color and flavor.
Notes
Serve skewered on toothpicks with extra teriyaki sauce for dipping.