Step 1: Preheat the oven to 400°F (200°C) for even cooking.
Step 2: In a large mixing bowl, combine ground beef, green onions, garlic, egg, panko, gochujang, ginger, soy sauce, and salt. Mix until just combined.
Step 3: Form the mixture into meatballs, about 1 to 1.5 inches in diameter, and place them on a parchment-lined baking sheet.
Step 4: Bake for 15-20 minutes until cooked through, reaching an internal temperature of 160°F (71°C).
Step 5: While baking, whisk rice vinegar, brown sugar, and soy sauce with gochujang in a saucepan over medium heat. Simmer for about 5 minutes.
Step 6: Brush the baked meatballs with the sauce or toss them gently to coat.
Step 7: Serve warm, garnished with sliced green onions, and enjoy with rice or as a snack!