In a large bowl, combine the ground beef, breadcrumbs, green onions, soy sauce, brown sugar, sesame oil, garlic, ginger, black pepper, and egg. Mix until well combined.
Shape the mixture into 1-inch meatballs and place them on a baking sheet.
Heat the vegetable oil in a large skillet over medium heat. Add the meatballs in batches, cooking for about 5-7 minutes, turning occasionally until browned and cooked through.
While the meatballs are cooking, 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 cooked, remove them from the skillet and serve warm with the spicy mayo dip.