The loaf that Steve Sullivan developed while working at Chez Panisse and refining his craft in the early 1980s, drawing on French artisan bakery traditions. The levain is a sourdough leavened entirely by a wild-yeast starter rather than commercial yeast, with a thick crust, open crumb and a flavor depth that was new to American bakeries when Sullivan introduced it in 1983. This bread supplies Chez Panisse and dozens of the Bay Area's best restaurants. The retail window at the San Pablo Avenue production bakery sells it directly from 08:00 Monday through Saturday until sellout.