01 - Set oven to 425°F and line a baking sheet with parchment paper.
02 - Mix ground beef, egg, breadcrumbs, garlic, spring onions, soy sauce, salt, and black pepper in a large bowl until just combined to retain tenderness.
03 - Form the mixture into 20 to 24 evenly sized meatballs and place them in a single layer on the prepared sheet.
04 - Bake for 12 to 15 minutes until fully cooked and well-browned.
05 - While meatballs bake, combine hot sauce, brown sugar, honey, apple cider vinegar, soy sauce, and sriracha in a saucepan over medium heat; bring to a simmer, stirring until sugar dissolves.
06 - Reduce heat and blend in butter until fully melted, whisking until glossy.
07 - Transfer baked meatballs to a large bowl, pour hot sauce over, and toss gently to coat all sides.
08 - Garnish meatballs with sesame seeds and sliced spring onions; serve immediately.