Preheat oven to 400°F (200°C) and line a baking sheet with parchment paper.,In a large bowl, gently mix ground beef, breadcrumbs, egg, garlic, ginger, soy sauce, sesame oil, green onions, brown sugar, and black pepper until just combined.,Shape mixture into 1½-inch meatballs and place evenly on the prepared baking sheet.,Bake for 18–20 minutes or until internal temperature reaches 160°F (71°C).,While baking, prepare glaze: In a saucepan over medium heat, combine soy sauce, brown sugar, honey, rice vinegar, gochujang, sesame oil, and garlic. Bring to a simmer.,Stir in cornstarch slurry and cook 1–2 minutes until thickened. Remove from heat.,Toss cooked meatballs in warm glaze until evenly coated.,In a small bowl, whisk together mayonnaise, gochujang, lemon juice, and honey for the dip.,Serve meatballs warm with spicy mayo on the side.