Preheat your oven to 400°F (200°C). Line a large baking sheet with parchment paper for easy cleanup.

In a large bowl, add the ground beef, panko breadcrumbs, egg, sliced green onions, 2 cloves of minced garlic, 1 tsp of grated ginger, and 1 tbsp of soy sauce. Use your hands to gently combine all ingredients, but be careful not to overmix.

Roll the mixture into approximately 1.5-inch meatballs and arrange them in a single layer on the prepared baking sheet. Bake for 15-20 minutes, or until cooked through and lightly browned.

While the meatballs are in the oven, combine the gochujang, 1/4 cup soy sauce, brown sugar, rice vinegar, sesame oil, remaining garlic, and remaining ginger in a medium saucepan. Whisk to combine and bring to a simmer over medium heat.

In a small bowl, mix the cornstarch with 1 tablespoon of cold water to create a slurry. Whisk the slurry into the simmering sauce and cook for 1-2 minutes more, until the glaze has thickened.

Remove the meatballs from the oven and carefully add them to the saucepan with the glaze. Gently toss to coat each meatball completely. Garnish with sesame seeds and extra sliced green onions before serving.