Combine the gin, limoncello, lemon juice, and mint leaves in a cocktail shaker. Fill 2/3 with ice and shake for 30 seconds.
Strain the cocktail into two martini glasses, preferably chilled.
Garnish as desired with lemon peels, lemon wedges, and mint leaves.
If desired, turn this into a cocktail by adding club soda and serving in a rocks or collins glass with ice.If possible, chill the martini glasses for at least 30 minutes in the freezer before serving to help keep the cocktail cool.Fresh lemon juice is best.