01 - Pour the heavy cream into a medium saucepan and add the granulated sugar. Place over medium heat, stirring gently until the sugar completely dissolves.
02 - Bring the cream mixture to a gentle boil, then reduce heat to maintain a steady simmer. Cook for exactly 3 minutes, stirring occasionally to prevent scorching or overflow.
03 - Remove the saucepan from heat immediately. Stir in the fresh lemon zest and juice, mixing thoroughly until fully incorporated. Let cool for 5 minutes.
04 - For a silkier texture, strain the mixture through a fine sieve into a pitcher to remove the zest bits. Pour evenly into 4 small serving glasses or ramekins.
05 - Refrigerate for at least 3 hours, or until the possets are firm and set to the touch.
06 - Top each posset with fresh berries and mint leaves just before serving.