Combine gin, syrup, and lemon juice in a cocktail shaker filled with ice. Shake vigorously and strain into an iced champagne glass. Top up with Champagne. Stir gently.
French 75 is a cocktail made from gin, Champagne, lemon juice, and sugar.
The drink was created in 1915 at the New York Bar in Paris—later Harry's New York Bar—by barman Harry MacElhone. The combination was said to have such a kick that it felt like being shelled with the powerful French 75mm field gun, also called a "75 Cocktail", or "Soixante Quinze" in French. The French 75 was popularized in America at the Stork Club in New York.