01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - Combine ground beef, egg, breadcrumbs, garlic, spring onions, soy sauce, salt, and pepper in a large mixing bowl. Mix gently until just incorporated.
03 - Portion mixture into 20 to 24 small balls, rolling gently, and arrange evenly on the prepared baking sheet.
04 - Transfer to oven and bake for 12 to 15 minutes, until meatballs are browned and cooked through.
05 - While meatballs bake, combine hot sauce, brown sugar, honey, apple cider vinegar, soy sauce, and sriracha in a saucepan over medium heat. Stir frequently and bring to a gentle simmer, ensuring the sugar dissolves.
06 - Lower heat and stir in unsalted butter until melted and the sauce becomes glossy.
07 - Transfer cooked meatballs to a large bowl. Pour warm firecracker sauce over and toss until evenly coated.
08 - Sprinkle with sesame seeds and sliced spring onions. Serve immediately.