Mix lime juice, gin, and superfine sugar in a 2-quart pitcher; chill until ready to serve, several hours.Advertisement
To serve, dip rims of glasses in lime juice, then sanding sugar, to coat with 1-inch-wide band. Measure 4 ounces Champagne into cocktail shaker filled with ice. Add 3 1/2 ounces lime juice-and-gin mixture, and shake; strain into 2 glasses, and add 2 to 3 drops of grenadine to each. Repeat.
To make this drink on demand, use the amounts in parentheses, and mix two drinks at once in a cocktail shaker filled with ice, then pour into glasses, and add grenadine. For a crowd, follow the directions below.