01 - In a small saucepan, whisk together lemon juice, zest, granulated sugar, water, and cornstarch until fully dissolved.
02 - Heat the mixture over medium heat, stirring constantly until thickened and glossy, approximately 3 to 4 minutes. Remove from heat and allow to cool to room temperature.
03 - Using an electric mixer or hand whisk, whip cold heavy cream with powdered sugar and vanilla extract until soft peaks form.
04 - Fold half of the whipped cream gently into the cooled lemon base until smooth and fully incorporated.
05 - Distribute the lemon-cream mixture evenly into four dessert glasses. Refrigerate for at least two hours to chill.
06 - Top each serving with the remaining whipped cream, a sprinkle of lemon zest, and fresh mint leaves if desired. Serve chilled.