from The American Bar
Place sugar cube into a champagne flute and saturate with Angostura. Add an ice cube, pour in Dubonnet, and fill with champagne. Add lemon twist.
from The Savoy Cocktail Book
Put 1 lump of sugar in a medium-sized wine-glass, 2 dashes of Secrestat Bitter poured on to the sugar, 1 lump of ice, quarter of a glass of Dubonnet, fill remainder with Champagne, squeeze lemon peel on top and stir slightly.