Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.

In a large bowl, combine the ground beef, panko breadcrumbs, egg, half of the green onions, half of the garlic, half of the ginger, 1 tablespoon of soy sauce, and sesame oil. Mix until just combined, being careful not to overwork the meat.

Form the mixture into meatballs, about 1 inch in diameter, and place them on the prepared baking sheet.

In a separate bowl, whisk together the remaining soy sauce, Gochujang, brown sugar, rice vinegar, and the remaining garlic and ginger to create a sauce.

Brush or drizzle half of the sauce over the meatballs, ensuring they are well coated.

Bake in the preheated oven for about 20 minutes, or until the meatballs are cooked through and lightly browned.

Remove from the oven and drizzle the remaining sauce over the meatballs, then sprinkle with sesame seeds and the rest of the green onions.

If desired, garnish with chopped cilantro before serving.