The origin of the champagne cocktail is dated to the mid-1800s consisting of a sugar cube soaked in aromatic bitters, cognac and topped up with champagne. 

The recipe for the cocktail appears in Jerry Thomas 1862 Bon Vivant’s Companion, which omits the brandy or cognac and is considered to be the classic American version.

Harry Johnson was one of the bartenders who revived the cocktail adding fruit to the mix.

Note to don’t crush the sugar cube, the whole point isn’t so much to sweeten the drink as to create bubbles, which the cube will do as it slowly dissolves.