Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin pan.
In a large bowl, combine the ground turkey, cooked brown rice, egg, panko, 3 tablespoons of the green onions, 2 tablespoons of the teriyaki sauce, ginger, garlic powder, and black pepper. Mix gently until everything is evenly combined.
Divide the mixture among the 8 prepared muffin cups. Press it in lightly, leaving the tops slightly rounded.
Bake for 20 minutes. Spoon the remaining teriyaki sauce over the muffins, then bake for 5 to 10 minutes more, until cooked through.
Let the muffins rest in the pan for 5 minutes. Sprinkle with the sesame seeds and remaining green onions before serving.