In a saucepan, combine the heavy cream, granulated sugar, and lemon zest. Cook over medium heat, stirring occasionally until the sugar dissolves and the mixture is warm but not boiling.

Remove the saucepan from heat. Stir in the fresh lemon juice and vanilla extract until fully combined.

Pour the mixture into individual serving cups or a large bowl. Allow it to cool to room temperature and then transfer it to the refrigerator. Let it chill for at least 4 hours or until set.

Once set, sprinkle an even layer of sugar on top of each posset. Using a kitchen torch (or by broiling in the oven), carefully caramelize the sugar until it forms a hard, glassy crust.

Allow the caramel to cool briefly before serving. Enjoy!