Ingredients :

• Lean ground beef — The “lean” isn’t a dietary whim — with beef that is too fatty, the tray ends up drowned in grease and the meatballs sit in their juices instead of browning. 5% fat is ideal. Ground chicken or turkey also work, but you must aim for 74°C internal temperature.
• Panko — No classic breadcrumbs here if you can avoid it. Panko is a coarser, lighter Japanese breadcrumb that gives the meatball a completely different texture — less compact, airier. It can be found in most supermarkets in the international aisle.
• Kewpie Mayo — Japanese Kewpie mayo is richer and more umami than classic mayo, with a slight concentrated egg taste that brings depth to the sauce. If you can’t find it, regular mayo works. A splash of lime juice in the sauce helps compensate.
• Sriracha — The spice level varies by brand. The classic rooster bottle — Huy Fong — is fruity and relatively mild. Others are much more violent. Start with the indicated amount, taste, and adjust. Since the sauce is prepared before the meatballs, you have plenty of time to calibrate.