You've overstocked on Champagne for midnight toasting at your big New Year's Eve soiree. But what to offer guests who crave something more on the order of a mixed drink? Fear not. One of the makings of delicious mixtures is already chilling on ice. Great cocktails built with Champagne and other sparkling wines have such an illustrious tradition that they should fit in well with anyone's sense of auld lang syne. Wine Spectator's Jack Bettridge provides some guidance.