Combine ground beef, Shaoxing wine, soy sauce, chili flakes, brown sugar, garlic, and ginger. Beat until sticky and bouncy. Add breadcrumbs, egg, and green onions. Mix until incorporated.
Form mixture into 24 heaping tablespoon-sized meatballs. Grease palms with oil to prevent sticking.
Mix brown sugar, soy sauce, water, garlic, and ginger in small bowl until sugar dissolves.
Combine cornstarch and water in small bowl. Mix well and set aside.
Heat skillet over medium-high with 1 teaspoon oil. Add meatballs with space between. Cook without touching until bottom browns, then flip 2-3 times until golden on most sides, about 8-10 minutes total.
Turn to medium heat. Move meatballs to one side and remove excess fat from pan.
Pour sauce into pan. Cook 2 minutes while stirring to coat meatballs evenly.
Turn to medium-low. Stir slurry to dissolve, swirl into pan. Stir immediately until sauce thickens, 1-2 minutes. Remove from heat.
Garnish with sliced green onions and serve hot over rice.
Notes
Use 80/20 or 85/15 beef for juiciest texture. Super lean meat makes dry meatballs.