Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper or lightly grease it.
In a large bowl, combine the ground turkey, breadcrumbs, chopped green onions, beaten egg, minced garlic, minced ginger, soy sauce, sesame oil, salt, and pepper. Mix until just combined, being careful not to overwork the meat.
Form the mixture into meatballs, about 1 inch in diameter, and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 15-20 minutes or until they're golden brown and cooked through (internal temperature should reach 165°F or 75°C).
While the meatballs are baking, heat the teriyaki sauce in a small saucepan over medium heat until it starts to simmer. Allow it to thicken slightly, about 3-5 minutes. If desired, you can add a teaspoon of cornstarch dissolved in a tablespoon of water for extra thickness.
Once the meatballs are done, transfer them to a large bowl and pour the warm teriyaki sauce over the top. Gently toss the meatballs in the sauce until they are fully coated.
Serve the teriyaki glazed turkey meatballs warm, garnished with sesame seeds and additional chopped green onions.
Notes
For extra thickness, add cornstarch to the teriyaki sauce.