Cut the lemons in half and carefully scoop out the pulp with a spoon.
Juice the pulp through a strainer and set the hollowed-out lemon halves aside.
Heat a saucepan and add sugar and cream. Stir until the sugar has dissolved.
Lower the heat and add the lemon juice and vanilla extract. Whisk for about 3 minutes. Remove the mixture from heat and let it cool for about an hour.
Fill the hollowed-out lemon halves with the cream mixture and freeze for about 2 hours, or until set.
Sprinkle lemon zest and top with mint leaves just before serving.