Prep your oven or pan. For baking, preheat to 400°F (200°C) and line a sheet pan with parchment. For stovetop, heat a large skillet over medium with 1 tablespoon oil.
Mix the meatball base. In a large bowl, whisk the egg with milk, soy sauce, sesame oil, garlic, ginger, salt, and pepper. Stir in green onions and breadcrumbs until evenly moistened.
Add the turkey. Gently fold in the ground turkey just until combined.
Don’t overwork it or the meatballs will be dense.
Shape the meatballs. With damp hands or a small scoop, form 1 to 1 1/4-inch balls. Aim for 20–24 meatballs so they cook evenly.
Cook the meatballs. To bake: Arrange on the prepared sheet pan and bake 14–16 minutes, until cooked through (internal temp 165°F/74°C) and lightly browned.
To pan-sear: Add meatballs to the hot skillet in a single layer. Sear 2–3 minutes per side until browned, then reduce heat to medium-low and cover for 4–6 minutes, turning as needed, until cooked through.
Make the sauce. In a small saucepan, combine honey, soy sauce, garlic, vinegar, and red pepper flakes.
Bring to a gentle simmer over medium heat. Whisk in the cornstarch slurry and simmer 1–2 minutes until glossy and slightly thickened.
Glaze the meatballs. Add cooked meatballs to the sauce (or pour the sauce into the skillet). Toss to coat and simmer 1–2 minutes so the sauce clings.
Finish and serve. Top with sesame seeds and green onions.
Serve over rice or noodles with veggies on the side.