How do you follow up a smash like St. Germain?Well, if you are Robert Cooper???the creator of that industry-wowing, elderflower-informed liqueur, which has become a staple behind every hip bar over the past two years???you do it with Creme Yvette.Creme Yvette was a defunct proprietary liqueur made from parma violet petals, berries, vanilla and other flavors and spices.