Place the cream, sugar en zest in a thick-based saucepan over medium-low heat and stir until the sugar dissolves. Boil gently for three minutes, then remove from the heat. Stir in the lemon juice. The acid interacts with the dairy quickly, so you’ll notice it starting to thicken almost immediately. Now for the very important part… Do NOT pour the posset mixture into your individual serving glasses right away. If you do, there is a great chance that it will separate, leaving you with a waxy, buttery layer on top and a watery lemon layer beneath it – pretty much the exact opposite of what you want.
To prevent this, pour the mixture into a large bowl and allow it to cool to room temperature. Stir it once or twice with a balloon whisk as it cools. Once it’s at room temperature, the lemon posset mixture will be velvety and smooth and ready to spoon into tiny glasses or espresso cups without the danger of separating. Pop the teeny glasses of posset in the fridge and chill for at least four hours before serving.
You want to serve this silky lemon posset with something crunchy for texture contrast. Now I could say be fancy and make lavender shortbread because lavender and lemon is a marriage made in heaven. But I seriously do not see the point in whipping up a 3-minute pudding and then spending an hour making biscuits. Nope, I go to the shops and buy ginger biscuits or good old Nuttikrust.