Of all the great mixed drinks featuring sparkling wine, the aptly named Champagne Cocktail is the most elegant and classic. Requiring just three ingredients and no shaking or stirring, it's the perfect serve for celebrations. Festive and tasty, the quality to effort ratio here is strong.
More or less an Old Fashioned but made with sparkling wine, cocktail bitters really get to shine here. They add a burst of flavor and spice, but the real joy is watching the jubilant stream of bubbles rise from the bottom of the glass as the wine slowly dissolves the sugar cube.
(Note that classically Aromatic bitters would be called for, but you can use whichever flavor of All The Bitter you like.)