Preheat the oven to 400°F.
In a large bowl, combine the ground beef, breadcrumbs, green onions, garlic, soy sauce, sesame oil, brown sugar, ginger, black pepper, and beaten egg. Mix until well combined.
Using your hands, form the mixture into meatballs, about 1 inch in diameter.
Place the meatballs on a baking sheet lined with parchment paper.
Bake for 20-25 minutes, or until cooked through and browned.
While the meatballs are baking, prepare the spicy mayo dip by mixing the mayonnaise, sriracha, lime juice, and garlic powder in a small bowl until smooth.
Once the meatballs are done, serve them hot with the spicy mayo dip on the side.