I know, sounds silly, but my brother once made me the best meatballs ever ... and refused to tell me what was in them.
Me, I just use hamburg, onions, seasoning, egg, bread crumbs.
I used half pork and hamburg one time, and then pork, veal and hamburg, but still haven't been able to come close to his! Can't ask him now, but I still keep trying different recipes.
Thanks.