01 - Preheat oven to 425°F (220°C). Line a baking sheet with parchment paper to prevent sticking.
02 - In a large bowl, gently blend ground beef, egg, breadcrumbs, minced garlic, chopped spring onions, soy sauce, salt, and black pepper until just incorporated. Avoid overmixing to maintain tenderness.
03 - Form the mixture into 20 to 24 uniform meatballs and arrange them evenly on the prepared baking sheet.
04 - Transfer the baking sheet to the oven and bake for 12 to 15 minutes, or until the meatballs are cooked through and evenly browned.
05 - While meatballs bake, combine hot sauce, brown sugar, honey, apple cider vinegar, soy sauce, and sriracha (if using) in a saucepan. Bring to a simmer over medium heat, stirring until the sugar dissolves.
06 - Reduce heat and whisk in the unsalted butter until melted and the sauce achieves a glossy consistency.
07 - Once meatballs are cooked, transfer them to a large bowl. Pour the hot firecracker sauce over the meatballs and gently toss to ensure an even coating.
08 - Arrange meatballs on a serving platter. Sprinkle with sesame seeds and sliced spring onions. Serve immediately.