Blitz the biscuits in a food processor and add the melted butter and mix together until combined
Alternatively, bash the biscuits to a fine crumb in a bowl and mix in the melted butter
Push the biscuits base into the bottom and sides of a loose bottomed 9" tart tin. I usually start on the sides, and then cover the bottom last.
Pour the double cream and caster sugar into a large pan and heat on the hob gently, stir until the sugar has dissolved.
Turn the heat up (medium heat max!) and heat the mixture until it starts to boil gently, stir frequently to stop the mixture from catching on the bottom – let it boil for 1 minute and then turn off the heat.
Stir in the lemon zest and juice and pour onto the biscuit base – refrigerate for 4+ hours, or preferably overnight so it has time to set properly.
Once set, decorate how you please – I mix 150ml double cream with 2 tbsps icing sugar and pipe on, and then use some freeze dried raspberries, and some biscuit crumbs.
Notes
You can obviously just make this in to individual Posset's leaving out the biscuit base, or even serve them individually! If I do that, I usually make 8-10 portions of of this mixture! Or if you go mini, use shot glasses!