Combine the gin, elderflower, and lemon juice in a mason jar without ice and refrigerate until ready to serve.
When it is time to serve the drinks, transfer the mixture to a shaker filled with ice (or simply add ice to the mason jar), shake for 30 seconds, and pour into flutes.
Top each flute with sparkling wine and serve.
Best sparkling wine for CocktailsDon't feel like you need to limit yourself to a French Champagne for this drink. You can also use a quality American sparkling wine, Italian Prosecco, or Spanish Cava. You'll find solid choices anywhere between the $15-20 range.The key is to make sure your sparkling wine is very dry. The liqueur adds a bit of sweetness to the drink, so if your wine is already somewhat sweet, your cocktail will be too sweet.