Juice the lemons and strain. Optionally, zest a lemon for garnish.
In a medium saucepan, combine the cream, ginger, and the sugar.
Bring mixture to a boil, stirring to dissolve the sugar. Continue boiling over medium heat until the mixture reduces to 2 cups. This will take about 10 minutes. Watch that the cream does not boil over. Pour the cream mixture into a 2-cup meauring cup to make sure it is at or close to 2 cups. If not, return the cream to the saucepan and continue boiling.
When the mixture is reduced to two cups, remove the saucepan from the heat and pour into a bowl then stir the lemon juice into the cream mixture.
Let the mixture cool for 15 minutes then strain the cream through a mesh strainer into a bowl or measuring cup.
Pour the custard into 4 ramekins, then refrigerate for two hours or until set.
You can leave the posset as is or top it with raspberries and lemon zest.
