01 - Preheat oven to 425°F (220°C) and line a baking sheet with parchment paper.
02 - In a large mixing bowl, combine ground beef, egg, breadcrumbs, minced garlic, finely chopped spring onions, soy sauce, salt, and black pepper. Gently mix just until combined to maintain a tender texture.
03 - Portion and shape the mixture into 20 to 24 evenly sized meatballs and arrange on the prepared baking sheet.
04 - Bake in the preheated oven for 12 to 15 minutes until cooked through and the exterior is nicely browned.
05 - As the meatballs bake, place hot sauce, brown sugar, honey, apple cider vinegar, soy sauce, and sriracha (if using) in a saucepan over medium heat. Whisk to combine and bring to a gentle simmer, stirring until the sugar is fully dissolved.
06 - Reduce the heat to low and add unsalted butter, stirring until fully melted and the sauce is glossy.
07 - Transfer baked meatballs to a large bowl, pour over the hot firecracker sauce, and toss to coat the meatballs evenly.
08 - Arrange coated meatballs on a platter and top with sesame seeds and sliced spring onions. Serve immediately.