1. For the lemon posset: place the double cream and caster sugar in a saucepan and heat over medium heat, stirring constantly, until the sugar has dissolved. Add the lemon zest and juice to the saucepan, and continue to stir until the mixture comes to a gentle boil. Remove the saucepan from the heat and let the mixture cool for a few minutes. Strain the mixture through a sieve and pour into serving glasses. You can also allow it to set in a bowl and spoon it into dishes. Set in the fridge for three hours.

2. For the macerated rhubarb: place the sliced rhubarb, caster sugar, vanilla pod and orange juice in a bowl and mix well. Cover the bowl with cling film and let the mixture sit at room temperature for at least an hour, or until the rhubarb has released its juices and softened.

3. For the shortbread biscuits: preheat the oven to 180 degrees. Cream the softened butter and caster sugar together in a mixing bowl until light and fluffy. Add the plain flour and salt to the bowl, and mix until a dough forms. Roll the dough out on a floured surface to a thickness of about one centimetre. Cut the dough into squares and place on a baking tray lined with parchment paper. Bake the biscuits for 12 minutes, or until light golden brown in colour. Remove the biscuits from the oven and let them cool on the baking tray.

4. Serve the lemon posset with a spoonful of macerated rhubarb and a shortbread biscuit crumbled on top.