For the past few years, bone marrow has been popping up on San Francisco restaurant menus. For instance, Poleng Lounge serves it along with wedges of coconut bread; Tartine pairs it with its legendary country loaf; and Serpentine actually serves up gamey buffalo bone marrow. But Chapeau! out on Clement offers the sort of marrow that could convert even the meat-adverse. Served with its rib roast, a gluttonous dish for two that comes with four sauces — blue cheese, peppercorn, béarnaise, and some more traditional truffle sauce — these are the sort of bones no one would make any bones about. And if you have a hungry pooch, your leftovers make for the best doggy bag of all time.