Preheat your oven to 400°F. Line a baking sheet with parchment paper.
In a large bowl, combine the ground beef, panko breadcrumbs, green onions, soy sauce, sesame oil, garlic, ginger, black pepper, red pepper flakes (if using), egg, and brown sugar. Mix until well combined.
Using your hands, form the mixture into meatballs about 1 inch in diameter and place them on the prepared baking sheet.
Bake the meatballs in the preheated oven for 20-25 minutes, or until cooked through and browned.
While the meatballs are baking, prepare the spicy mayo dip by whisking together the mayonnaise, sriracha, lime juice, and honey in a small bowl. Adjust the sriracha to taste for desired spice level.
Once the meatballs are done, remove them from the oven and let them cool slightly before serving with the spicy mayo dip.