Gin and Champagne make a bubbly wonderful duo, which is why this classic cocktail is always a good idea.
Combine gin, lemon juice, and simple syrup in a cocktail shaker. Fill shaker with ice, cover, and shake vigorously until outside of shaker is very cold, about 20 seconds.
Strain cocktail through a Hawthorne strainer or a slotted spoon into a large flute. Top with Champagne; garnish with lemon twist.
2 ounces London dry gin
¾ ounce fresh lemon juice
¾ ounce simple syrup
2 ounces Champagne
Long spiral lemon twist (for serving)