Place gin, lemon juice, and simple syrup in an ice filled cocktail shaker. Shake vigorously, then strain into a glass. Top with champagne and garnish with a lemon twist. Ingredients can easily be adjusted to suit your taste, feel free to use more or less.
Notes
*To make simple syrup: combine ½ cup water and ½ cup granulated sugar in a small saucepan. Bring to a boil, stirring occasionally, until the sugar is dissolved. Transfer into a sealed container and chill. Leftovers can be stored in the refrigerator for up to 2 weeks.