Chill the glass: fill champagne flutes with ice and cold water. Let it sit while gathering the ingredients. Empty the glasses before making the cocktail.
Pour liqueur into the champagne flute.
Fill the glass with champagne slowly.
Garnish with raspberries, blackberries, or a lemon twist.
Serve right away.
Notes
Note: if using Crème de Cassis, use about 1/2 oz. because it is much sweeter and more syrupy than Chambord.