Sonny's is what you might call an institution — by the time its birthday rolls around on May 29, it will have been sitting in the same quaint spot just north of Taft Street for 50 years. It's a family joint, with papa Sonny having passed down his legacy to his sonny, John Nigro, who's continued the fine tradition of honest, blue-collar food prepared exactingly. And although Sonny's is best known for its Philadelphia-style steak hogies (not "hoagies"), cut from rib eye beef and wedged into a housemade roll, they also serve one mean hamburger. They call it a hogie burger: An oblong, griddle-cooked patty of freshly ground beef that fits nicely on one of Sonny's famous hogie rolls. And it's nearly perfect. The burger is immensely beefy and charred on an age-old griddle. When you bite into it, the thing drips with a slurry of rendered fat, most of which gets soaked up by the luscious, cornmeal-studded roll. A 6-ounce burger will set you back only $3.75, and it's a meal on its own. Slather it with sweet, pickled peppers provided at every table, or add cheese for just $.50. Either way, it's a beef sandwich worth returning for, be it tomorrow or 50 years from now.