Preheat the Oven:Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper.
Make the Meatball Mixture:In a large bowl, combine ground beef, soy sauce, sesame oil, brown sugar, garlic, ginger, green onions, egg, breadcrumbs, gochugaru (if using), and black pepper. Mix gently just until combined.
Form the Meatballs:Scoop and roll the mixture into 1½-inch meatballs. Place them evenly spaced on the prepared baking sheet.
Bake:Bake for 15–20 minutes, or until the meatballs are cooked through and lightly browned.
Prepare the Spicy Mayo Dip:While the meatballs bake, whisk together mayonnaise, sriracha, rice vinegar, sesame oil, honey, soy sauce, and lime juice in a small bowl. Taste and adjust seasoning as needed.
Serve:Serve the warm meatballs with the spicy mayo dip on the side or drizzled over the top. Garnish with additional green onions if desired.