Top with 4-6 oz of sparkling water, adjusting the amount based on preferred strength.
Gently stir with a bar spoon to combine.
If desired, garnish with a fresh lemon twist.
Notes
The drink works best with chilled ingredients. Store limoncello in the freezer for an extra cold cocktail.A standard ratio is 1 part limoncello to 2-3 parts sparkling water. Adjust this ratio to taste.Plain sparkling water works great, but lemon-flavored sparkling water adds extra citrus notes.The cocktail can be made in larger batches for parties. Mix limoncello and sparkling water just before serving to maintain carbonation