In a large bowl, combine the ground beef, panko, beaten egg, minced garlic, grated ginger, soy sauce, gochujang, brown sugar, sesame oil, salt, pepper, and chopped green onions. Use your hands to mix gently until just combined. Overmixing will make the meatballs dense and tough. Cover and refrigerate for 15-20 minutes. This resting step allows the breadcrumbs to absorb moisture and makes rolling much easier.
Line a rimmed baking sheet with parchment paper. Using a small cookie scoop or your palms, roll the mixture into smooth, uniform balls about 1 to 1.5 inches (2.5 to 3.8 cm) in diameter. Uniform sizing ensures even cooking. You should get approximately 20 to 24 meatballs.
Oven-Baking Method (Recommended): Preheat your oven to 400°F (200°C). Arrange the meatballs on the prepared baking sheet with a little space between each. Bake for 18-22 minutes, or until the internal temperature reaches 165°F (74°C) and the outsides are golden brown.Air Fryer Method: Preheat your air fryer to 375°F (190°C). Lightly spray the basket with oil and arrange meatballs in a single layer without crowding (cook in batches if needed). Air fry for 10-12 minutes, shaking the basket halfway through, until cooked through and nicely browned.Pan-Frying Method: Heat a large skillet over medium heat with 1 tablespoon of oil. Add meatballs in a single layer and cook for 10-12 minutes, turning occasionally, until browned on all sides and cooked through. While the meatballs cook, prepare the glaze. In a small saucepan, combine the soy sauce, honey (or brown sugar), gochujang, rice vinegar, sesame oil, minced garlic, and grated ginger. Whisk together over medium heat until smooth. Bring to a gentle simmer, then reduce the heat to low. Stir in the cornstarch slurry and cook for 2-3 minutes, stirring constantly, until the glaze thickens and becomes glossy. Remove from heat.
Transfer the cooked meatballs to a large bowl. Pour the warm glaze over the top and toss gently until every meatball is thoroughly coated and glistening. For an extra-caramelized finish, spread the glazed meatballs on a baking sheet and broil for 1-2 minutes, watching closely to prevent burning.
In a small bowl, whisk together the mayonnaise, gochujang, lime juice, honey, and garlic powder until completely smooth and uniformly pink. Taste and adjust the heat level by adding more gochujang if desired. Cover and refrigerate until serving.
Arrange the glazed meatballs on a serving platter. Sprinkle generously with toasted sesame seeds and sliced green onions. Serve immediately with the spicy mayo dip on the side for dunking.