Blitz 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
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 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.
Decorate with whipped cream, some freeze dried raspberries, and some biscuit crumbs.
