01 - Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper.
02 - Combine ground beef, egg, breadcrumbs, minced garlic, chopped spring onions, soy sauce, salt, and black pepper in a mixing bowl. Gently fold the mixture just until ingredients are fully incorporated without overmixing.
03 - Portion and roll the mixture into 20 to 24 small balls. Arrange evenly on the prepared baking sheet.
04 - Bake for 12 to 15 minutes or until the meatballs are browned and thoroughly cooked.
05 - While meatballs bake, combine hot sauce, brown sugar, honey, apple cider vinegar, soy sauce, and sriracha if using in a saucepan over medium heat. Stir to dissolve the sugar and bring to a low simmer.
06 - Lower heat and swirl in unsalted butter until melted and the sauce turns glossy and uniform.
07 - Transfer hot meatballs to a large bowl. Pour firecracker sauce over the meatballs and toss gently to coat evenly.
08 - Arrange meatballs on a platter or individual plates. Sprinkle with sesame seeds and sliced spring onions. Serve immediately.