01 - Pour the heavy cream and granulated sugar into a medium saucepan. Place over medium heat and stir gently until the sugar completely dissolves.
02 - Bring the cream mixture to a gentle boil, then reduce heat and simmer for exactly 3 minutes. Stir occasionally to prevent scorching and watch carefully to avoid overflow.
03 - Remove the saucepan from heat immediately. Stir in the lemon zest and fresh lemon juice, mixing thoroughly until fully incorporated.
04 - Let the mixture cool for 5 minutes. For an ultra-smooth texture, strain through a fine-mesh sieve into a measuring cup or pitcher to remove the lemon zest bits.
05 - Divide the mixture evenly among 4 small serving glasses, ramekins, or dessert bowls. Wipe any drips from the rims for a clean presentation.
06 - Refrigerate for at least 3 hours, or until the posset is completely set and firm to the touch. The texture should be silky and hold its shape.
07 - Just before serving, top each posset with fresh berries and mint leaves. Serve chilled for the best texture and flavor experience.