01 - Preheat oven to 425°F. Line a baking sheet with parchment paper.
02 - In a large mixing bowl, combine ground beef, egg, breadcrumbs, minced garlic, chopped spring onions, soy sauce, salt, and black pepper. Mix gently until ingredients are just integrated without overworking the meat.
03 - Roll mixture into 20 to 24 evenly sized meatballs, placing them evenly spaced on the prepared baking sheet.
04 - Transfer baking sheet to the oven and bake for 12 to 15 minutes until meatballs are browned and fully cooked through.
05 - While meatballs are baking, combine hot sauce, brown sugar, honey, apple cider vinegar, soy sauce, and sriracha, if using, in a saucepan over medium heat. Stir and bring to a gentle simmer until sugar dissolves.
06 - Reduce heat and whisk in unsalted butter until melted and sauce is glossy and emulsified.
07 - Transfer baked meatballs to a large bowl. Pour hot firecracker sauce over and gently toss until the meatballs are fully coated.
08 - Arrange coated meatballs on a platter or serve immediately, garnished with sesame seeds and sliced spring onions.