Prepare the meatballs: Preheat oven to 400°F. Line a baking sheet with parchment paper. Add egg, breadcrumbs, turkey, cilantro, green onion, soy sauce, vegetable oil, sesame oil, and salt to a large bowl. Gently mix together with your hands until combined.
Roll tablespoon-size scoops between your palms to form meatballs and transfer to prepared baking sheet. You will have about 40. Bake until well browned, 20 to 25 minutes.
While meatballs bake, prepare the dipping sauce: Smash ginger with the heavy side of a knife and put in a small saucepan. Add brown sugar, soy sauce, and rice vinegar. Stir over medium-low heat until sugar dissolves and mixture is slightly thickened, about 3 minutes. Strain out ginger and transfer sauce to a bowl. Garnish with green onions, if using. Serve sauce with meatballs.
Give the younger set the option of dipping their meatballs in ketchup or barbecue sauce.