If serving the lemon posset without the cake, prepare a double recipe to make five ½ cup servings. After combining the cream and the lemon syrup and straining it into the 2 cup glass measure, pour equal amounts into five small ramekins or Pyrex custard cups. Refrigerate, uncovered, for 4 hours. Once the mixture is set, cover each ramekin tightly with plastic wrap. Let the possets sit for 10 minutes at room temperature before serving.