The coffee retailer announced that java aficionados in San Francisco will be among the first to taste cups of joe brewed by the high-end Clover brewing machines. Starbucks unveiled the machines in Seattle stores Tuesday, and said it will add it to sites in Boston and San Francisco in the coming months. The Clover machines make one cup at a time and aim to coax out each of the hundreds of flavors known to reside in the average coffee bean.