In a large mixing bowl, combine ground beef, panko breadcrumbs, egg, soy sauce, sesame oil, garlic, ginger, and half of the green onions. Mix gently for 2-3 minutes.

Shape the mixture into bite-sized meatballs, approximately 1 inch in diameter, and place on a clean plate.

Heat vegetable oil in a large skillet over medium heat until shimmering. Arrange meatballs in a single layer.

Cook the meatballs for 5-7 minutes, turning occasionally until browned and firm.

Whisk together gochujang, brown sugar, rice vinegar, and a splash of water in a bowl until smooth.

Pour the glaze over the meatballs in the skillet, tossing gently to coat and let it bubble for 2-3 minutes.

Transfer to a serving platter and sprinkle with toasted sesame seeds and remaining green onions.