Preheat oven to 400°F (200°C).
In a bowl, combine ground beef, garlic, half the green onions, salt, and pepper. Mix gently.
Form mixture into 16 meatballs and place on a baking sheet lined with parchment paper.
Bake meatballs for 12-15 minutes until cooked through.
Meanwhile, whisk soy sauce, brown sugar, water, and cornstarch in a small saucepan over medium heat.
Cook sauce, stirring constantly, until thickened.
Heat oil in a skillet over medium heat. Add baked meatballs and pour sauce over them.
Toss to coat and cook for 2-3 minutes.
Garnish with remaining green onions and serve hot.